// SPDX-License-Identifier: GPL-2.0-only
/*
 * VFIO PCI config space virtualization
 *
 * Copyright (C) 2012 Red Hat, Inc.  All rights reserved.
 *     Author: Alex Williamson <alex.williamson@redhat.com>
 *
 * Derived from original vfio:
 * Copyright 2010 Cisco Systems, Inc.  All rights reserved.
 * Author: Tom Lyon, pugs@cisco.com
 */

/*
 * This code handles reading and writing of PCI configuration registers.
 * This is hairy because we want to allow a lot of flexibility to the
 * user driver, but cannot trust it with all of the config fields.
 * Tables determine which fields can be read and written, as well as
 * which fields are 'virtualized' - special actions and translations to
 * make it appear to the user that he has control, when in fact things
 * must be negotiated with the underlying OS.
 */

#include <linux/fs.h>
#include <linux/pci.h>
#include <linux/uaccess.h>
#include <linux/vfio.h>
#include <linux/slab.h>

#include "vfio_pci_priv.h"

/* Fake capability ID for standard config space */
#define PCI_CAP_ID_BASIC        0

#define is_bar(offset)  \
        ((offset >= PCI_BASE_ADDRESS_0 && offset < PCI_BASE_ADDRESS_5 + 4) || \
         (offset >= PCI_ROM_ADDRESS && offset < PCI_ROM_ADDRESS + 4))

/*
 * Lengths of PCI Config Capabilities
 *   0: Removed from the user visible capability list
 *   FF: Variable length
 */
static const u8 pci_cap_length[PCI_CAP_ID_MAX + 1] = {
        [PCI_CAP_ID_BASIC]      = PCI_STD_HEADER_SIZEOF, /* pci config header */
        [PCI_CAP_ID_PM]         = PCI_PM_SIZEOF,
        [PCI_CAP_ID_AGP]        = PCI_AGP_SIZEOF,
        [PCI_CAP_ID_VPD]        = PCI_CAP_VPD_SIZEOF,
        [PCI_CAP_ID_SLOTID]     = 0,            /* bridge - don't care */
        [PCI_CAP_ID_MSI]        = 0xFF,         /* 10, 14, 20, or 24 */
        [PCI_CAP_ID_CHSWP]      = 0,            /* cpci - not yet */
        [PCI_CAP_ID_PCIX]       = 0xFF,         /* 8 or 24 */
        [PCI_CAP_ID_HT]         = 0xFF,         /* hypertransport */
        [PCI_CAP_ID_VNDR]       = 0xFF,         /* variable */
        [PCI_CAP_ID_DBG]        = 0,            /* debug - don't care */
        [PCI_CAP_ID_CCRC]       = 0,            /* cpci - not yet */
        [PCI_CAP_ID_SHPC]       = 0,            /* hotswap - not yet */
        [PCI_CAP_ID_SSVID]      = 0,            /* bridge - don't care */
        [PCI_CAP_ID_AGP3]       = 0,            /* AGP8x - not yet */
        [PCI_CAP_ID_SECDEV]     = 0,            /* secure device not yet */
        [PCI_CAP_ID_EXP]        = 0xFF,         /* 20 or 44 */
        [PCI_CAP_ID_MSIX]       = PCI_CAP_MSIX_SIZEOF,
        [PCI_CAP_ID_SATA]       = 0xFF,
        [PCI_CAP_ID_AF]         = PCI_CAP_AF_SIZEOF,
};

/*
 * Lengths of PCIe/PCI-X Extended Config Capabilities
 *   0: Removed or masked from the user visible capability list
 *   FF: Variable length
 */
static const u16 pci_ext_cap_length[PCI_EXT_CAP_ID_MAX + 1] = {
        [PCI_EXT_CAP_ID_ERR]    =       PCI_ERR_ROOT_COMMAND,
        [PCI_EXT_CAP_ID_VC]     =       0xFF,
        [PCI_EXT_CAP_ID_DSN]    =       PCI_EXT_CAP_DSN_SIZEOF,
        [PCI_EXT_CAP_ID_PWR]    =       PCI_EXT_CAP_PWR_SIZEOF,
        [PCI_EXT_CAP_ID_RCLD]   =       0,      /* root only - don't care */
        [PCI_EXT_CAP_ID_RCILC]  =       0,      /* root only - don't care */
        [PCI_EXT_CAP_ID_RCEC]   =       0,      /* root only - don't care */
        [PCI_EXT_CAP_ID_MFVC]   =       0xFF,
        [PCI_EXT_CAP_ID_VC9]    =       0xFF,   /* same as CAP_ID_VC */
        [PCI_EXT_CAP_ID_RCRB]   =       0,      /* root only - don't care */
        [PCI_EXT_CAP_ID_VNDR]   =       0xFF,
        [PCI_EXT_CAP_ID_CAC]    =       0,      /* obsolete */
        [PCI_EXT_CAP_ID_ACS]    =       0xFF,
        [PCI_EXT_CAP_ID_ARI]    =       PCI_EXT_CAP_ARI_SIZEOF,
        [PCI_EXT_CAP_ID_ATS]    =       PCI_EXT_CAP_ATS_SIZEOF,
        [PCI_EXT_CAP_ID_SRIOV]  =       PCI_EXT_CAP_SRIOV_SIZEOF,
        [PCI_EXT_CAP_ID_MRIOV]  =       0,      /* not yet */
        [PCI_EXT_CAP_ID_MCAST]  =       PCI_EXT_CAP_MCAST_ENDPOINT_SIZEOF,
        [PCI_EXT_CAP_ID_PRI]    =       PCI_EXT_CAP_PRI_SIZEOF,
        [PCI_EXT_CAP_ID_AMD_XXX] =      0,      /* not yet */
        [PCI_EXT_CAP_ID_REBAR]  =       0xFF,
        [PCI_EXT_CAP_ID_DPA]    =       0xFF,
        [PCI_EXT_CAP_ID_TPH]    =       0xFF,
        [PCI_EXT_CAP_ID_LTR]    =       PCI_EXT_CAP_LTR_SIZEOF,
        [PCI_EXT_CAP_ID_SECPCI] =       0,      /* not yet */
        [PCI_EXT_CAP_ID_PMUX]   =       0,      /* not yet */
        [PCI_EXT_CAP_ID_PASID]  =       0,      /* not yet */
        [PCI_EXT_CAP_ID_DVSEC]  =       0xFF,
};

/*
 * Read/Write Permission Bits - one bit for each bit in capability
 * Any field can be read if it exists, but what is read depends on
 * whether the field is 'virtualized', or just pass through to the
 * hardware.  Any virtualized field is also virtualized for writes.
 * Writes are only permitted if they have a 1 bit here.
 */
struct perm_bits {
        u8      *virt;          /* read/write virtual data, not hw */
        u8      *write;         /* writeable bits */
        int     (*readfn)(struct vfio_pci_core_device *vdev, int pos, int count,
                          struct perm_bits *perm, int offset, __le32 *val);
        int     (*writefn)(struct vfio_pci_core_device *vdev, int pos, int count,
                           struct perm_bits *perm, int offset, __le32 val);
};

#define NO_VIRT         0
#define ALL_VIRT        0xFFFFFFFFU
#define NO_WRITE        0
#define ALL_WRITE       0xFFFFFFFFU

static int vfio_user_config_read(struct pci_dev *pdev, int offset,
                                 __le32 *val, int count)
{
        int ret = -EINVAL;
        u32 tmp_val = 0;

        switch (count) {
        case 1:
        {
                u8 tmp;
                ret = pci_user_read_config_byte(pdev, offset, &tmp);
                tmp_val = tmp;
                break;
        }
        case 2:
        {
                u16 tmp;
                ret = pci_user_read_config_word(pdev, offset, &tmp);
                tmp_val = tmp;
                break;
        }
        case 4:
                ret = pci_user_read_config_dword(pdev, offset, &tmp_val);
                break;
        }

        *val = cpu_to_le32(tmp_val);

        return ret;
}

static int vfio_user_config_write(struct pci_dev *pdev, int offset,
                                  __le32 val, int count)
{
        int ret = -EINVAL;
        u32 tmp_val = le32_to_cpu(val);

        switch (count) {
        case 1:
                ret = pci_user_write_config_byte(pdev, offset, tmp_val);
                break;
        case 2:
                ret = pci_user_write_config_word(pdev, offset, tmp_val);
                break;
        case 4:
                ret = pci_user_write_config_dword(pdev, offset, tmp_val);
                break;
        }

        return ret;
}

static int vfio_default_config_read(struct vfio_pci_core_device *vdev, int pos,
                                    int count, struct perm_bits *perm,
                                    int offset, __le32 *val)
{
        __le32 virt = 0;

        memcpy(val, vdev->vconfig + pos, count);

        memcpy(&virt, perm->virt + offset, count);

        /* Any non-virtualized bits? */
        if (cpu_to_le32(~0U >> (32 - (count * 8))) != virt) {
                struct pci_dev *pdev = vdev->pdev;
                __le32 phys_val = 0;
                int ret;

                ret = vfio_user_config_read(pdev, pos, &phys_val, count);
                if (ret)
                        return ret;

                *val = (phys_val & ~virt) | (*val & virt);
        }

        return count;
}

static int vfio_default_config_write(struct vfio_pci_core_device *vdev, int pos,
                                     int count, struct perm_bits *perm,
                                     int offset, __le32 val)
{
        __le32 virt = 0, write = 0;

        memcpy(&write, perm->write + offset, count);

        if (!write)
                return count; /* drop, no writable bits */

        memcpy(&virt, perm->virt + offset, count);

        /* Virtualized and writable bits go to vconfig */
        if (write & virt) {
                __le32 virt_val = 0;

                memcpy(&virt_val, vdev->vconfig + pos, count);

                virt_val &= ~(write & virt);
                virt_val |= (val & (write & virt));

                memcpy(vdev->vconfig + pos, &virt_val, count);
        }

        /* Non-virtualized and writable bits go to hardware */
        if (write & ~virt) {
                struct pci_dev *pdev = vdev->pdev;
                __le32 phys_val = 0;
                int ret;

                ret = vfio_user_config_read(pdev, pos, &phys_val, count);
                if (ret)
                        return ret;

                phys_val &= ~(write & ~virt);
                phys_val |= (val & (write & ~virt));

                ret = vfio_user_config_write(pdev, pos, phys_val, count);
                if (ret)
                        return ret;
        }

        return count;
}

/* Allow direct read from hardware, except for capability next pointer */
static int vfio_direct_config_read(struct vfio_pci_core_device *vdev, int pos,
                                   int count, struct perm_bits *perm,
                                   int offset, __le32 *val)
{
        int ret;

        ret = vfio_user_config_read(vdev->pdev, pos, val, count);
        if (ret)
                return ret;

        if (pos >= PCI_CFG_SPACE_SIZE) { /* Extended cap header mangling */
                if (offset < 4)
                        memcpy(val, vdev->vconfig + pos, count);
        } else if (pos >= PCI_STD_HEADER_SIZEOF) { /* Std cap mangling */
                if (offset == PCI_CAP_LIST_ID && count > 1)
                        memcpy(val, vdev->vconfig + pos,
                               min(PCI_CAP_FLAGS, count));
                else if (offset == PCI_CAP_LIST_NEXT)
                        memcpy(val, vdev->vconfig + pos, 1);
        }

        return count;
}

/* Raw access skips any kind of virtualization */
static int vfio_raw_config_write(struct vfio_pci_core_device *vdev, int pos,
                                 int count, struct perm_bits *perm,
                                 int offset, __le32 val)
{
        int ret;

        ret = vfio_user_config_write(vdev->pdev, pos, val, count);
        if (ret)
                return ret;

        return count;
}

static int vfio_raw_config_read(struct vfio_pci_core_device *vdev, int pos,
                                int count, struct perm_bits *perm,
                                int offset, __le32 *val)
{
        int ret;

        ret = vfio_user_config_read(vdev->pdev, pos, val, count);
        if (ret)
                return ret;

        return count;
}

/* Virt access uses only virtualization */
static int vfio_virt_config_write(struct vfio_pci_core_device *vdev, int pos,
                                  int count, struct perm_bits *perm,
                                  int offset, __le32 val)
{
        memcpy(vdev->vconfig + pos, &val, count);
        return count;
}

static int vfio_virt_config_read(struct vfio_pci_core_device *vdev, int pos,
                                 int count, struct perm_bits *perm,
                                 int offset, __le32 *val)
{
        memcpy(val, vdev->vconfig + pos, count);
        return count;
}

static struct perm_bits direct_ro_perms = {
        .readfn = vfio_direct_config_read,
};

/* Default capability regions to read-only, no-virtualization */
static struct perm_bits cap_perms[PCI_CAP_ID_MAX + 1] = {
        [0 ... PCI_CAP_ID_MAX] = { .readfn = vfio_direct_config_read }
};
static struct perm_bits ecap_perms[PCI_EXT_CAP_ID_MAX + 1] = {
        [0 ... PCI_EXT_CAP_ID_MAX] = { .readfn = vfio_direct_config_read }
};
/*
 * Default unassigned regions to raw read-write access.  Some devices
 * require this to function as they hide registers between the gaps in
 * config space (be2net).  Like MMIO and I/O port registers, we have
 * to trust the hardware isolation.
 */
static struct perm_bits unassigned_perms = {
        .readfn = vfio_raw_config_read,
        .writefn = vfio_raw_config_write
};

static struct perm_bits virt_perms = {
        .readfn = vfio_virt_config_read,
        .writefn = vfio_virt_config_write
};

static void free_perm_bits(struct perm_bits *perm)
{
        kfree(perm->virt);
        kfree(perm->write);
        perm->virt = NULL;
        perm->write = NULL;
}

static int alloc_perm_bits(struct perm_bits *perm, int size)
{
        /*
         * Round up all permission bits to the next dword, this lets us
         * ignore whether a read/write exceeds the defined capability
         * structure.  We can do this because:
         *  - Standard config space is already dword aligned
         *  - Capabilities are all dword aligned (bits 0:1 of next reserved)
         *  - Express capabilities defined as dword aligned
         */
        size = round_up(size, 4);

        /*
         * Zero state is
         * - All Readable, None Writeable, None Virtualized
         */
        perm->virt = kzalloc(size, GFP_KERNEL);
        perm->write = kzalloc(size, GFP_KERNEL);
        if (!perm->virt || !perm->write) {
                free_perm_bits(perm);
                return -ENOMEM;
        }

        perm->readfn = vfio_default_config_read;
        perm->writefn = vfio_default_config_write;

        return 0;
}

/*
 * Helper functions for filling in permission tables
 */
static inline void p_setb(struct perm_bits *p, int off, u8 virt, u8 write)
{
        p->virt[off] = virt;
        p->write[off] = write;
}

/* Handle endian-ness - pci and tables are little-endian */
static inline void p_setw(struct perm_bits *p, int off, u16 virt, u16 write)
{
        *(__le16 *)(&p->virt[off]) = cpu_to_le16(virt);
        *(__le16 *)(&p->write[off]) = cpu_to_le16(write);
}

/* Handle endian-ness - pci and tables are little-endian */
static inline void p_setd(struct perm_bits *p, int off, u32 virt, u32 write)
{
        *(__le32 *)(&p->virt[off]) = cpu_to_le32(virt);
        *(__le32 *)(&p->write[off]) = cpu_to_le32(write);
}

/* Caller should hold memory_lock semaphore */
bool __vfio_pci_memory_enabled(struct vfio_pci_core_device *vdev)
{
        struct pci_dev *pdev = vdev->pdev;
        u16 cmd = le16_to_cpu(*(__le16 *)&vdev->vconfig[PCI_COMMAND]);

        /*
         * Memory region cannot be accessed if device power state is D3.
         *
         * SR-IOV VF memory enable is handled by the MSE bit in the
         * PF SR-IOV capability, there's therefore no need to trigger
         * faults based on the virtual value.
         */
        return pdev->current_state < PCI_D3hot &&
               (pdev->no_command_memory || (cmd & PCI_COMMAND_MEMORY));
}
EXPORT_SYMBOL_GPL(__vfio_pci_memory_enabled);

/*
 * Restore the *real* BARs after we detect a FLR or backdoor reset.
 * (backdoor = some device specific technique that we didn't catch)
 */
static void vfio_bar_restore(struct vfio_pci_core_device *vdev)
{
        struct pci_dev *pdev = vdev->pdev;
        u32 *rbar = vdev->rbar;
        u16 cmd;
        int i;

        if (pdev->is_virtfn)
                return;

        pci_info(pdev, "%s: reset recovery - restoring BARs\n", __func__);

        for (i = PCI_BASE_ADDRESS_0; i <= PCI_BASE_ADDRESS_5; i += 4, rbar++)
                pci_user_write_config_dword(pdev, i, *rbar);

        pci_user_write_config_dword(pdev, PCI_ROM_ADDRESS, *rbar);

        if (vdev->nointx) {
                pci_user_read_config_word(pdev, PCI_COMMAND, &cmd);
                cmd |= PCI_COMMAND_INTX_DISABLE;
                pci_user_write_config_word(pdev, PCI_COMMAND, cmd);
        }
}

static __le32 vfio_generate_bar_flags(struct pci_dev *pdev, int bar)
{
        unsigned long flags = pci_resource_flags(pdev, bar);
        u32 val;

        if (flags & IORESOURCE_IO)
                return cpu_to_le32(PCI_BASE_ADDRESS_SPACE_IO);

        val = PCI_BASE_ADDRESS_SPACE_MEMORY;

        if (flags & IORESOURCE_PREFETCH)
                val |= PCI_BASE_ADDRESS_MEM_PREFETCH;

        if (flags & IORESOURCE_MEM_64)
                val |= PCI_BASE_ADDRESS_MEM_TYPE_64;

        return cpu_to_le32(val);
}

/*
 * Pretend we're hardware and tweak the values of the *virtual* PCI BARs
 * to reflect the hardware capabilities.  This implements BAR sizing.
 */
static void vfio_bar_fixup(struct vfio_pci_core_device *vdev)
{
        struct pci_dev *pdev = vdev->pdev;
        int i;
        __le32 *vbar;
        u64 mask;

        if (!vdev->bardirty)
                return;

        vbar = (__le32 *)&vdev->vconfig[PCI_BASE_ADDRESS_0];

        for (i = 0; i < PCI_STD_NUM_BARS; i++, vbar++) {
                int bar = i + PCI_STD_RESOURCES;

                if (!pci_resource_start(pdev, bar)) {
                        *vbar = 0; /* Unmapped by host = unimplemented to user */
                        continue;
                }

                mask = ~(pci_resource_len(pdev, bar) - 1);

                *vbar &= cpu_to_le32((u32)mask);
                *vbar |= vfio_generate_bar_flags(pdev, bar);

                if (*vbar & cpu_to_le32(PCI_BASE_ADDRESS_MEM_TYPE_64)) {
                        vbar++;
                        *vbar &= cpu_to_le32((u32)(mask >> 32));
                        i++;
                }
        }

        vbar = (__le32 *)&vdev->vconfig[PCI_ROM_ADDRESS];

        /*
         * NB. REGION_INFO will have reported zero size if we weren't able
         * to read the ROM, but we still return the actual BAR size here if
         * it exists (or the shadow ROM space).
         */
        if (pci_resource_start(pdev, PCI_ROM_RESOURCE)) {
                mask = ~(pci_resource_len(pdev, PCI_ROM_RESOURCE) - 1);
                mask |= PCI_ROM_ADDRESS_ENABLE;
                *vbar &= cpu_to_le32((u32)mask);
        } else if (pdev->rom && pdev->romlen) {
                mask = ~(roundup_pow_of_two(pdev->romlen) - 1);
                mask |= PCI_ROM_ADDRESS_ENABLE;
                *vbar &= cpu_to_le32((u32)mask);
        } else {
                *vbar = 0;
        }

        vdev->bardirty = false;
}

static int vfio_basic_config_read(struct vfio_pci_core_device *vdev, int pos,
                                  int count, struct perm_bits *perm,
                                  int offset, __le32 *val)
{
        if (is_bar(offset)) /* pos == offset for basic config */
                vfio_bar_fixup(vdev);

        count = vfio_default_config_read(vdev, pos, count, perm, offset, val);

        /* Mask in virtual memory enable */
        if (offset == PCI_COMMAND && vdev->pdev->no_command_memory) {
                u16 cmd = le16_to_cpu(*(__le16 *)&vdev->vconfig[PCI_COMMAND]);
                u32 tmp_val = le32_to_cpu(*val);

                tmp_val |= cmd & PCI_COMMAND_MEMORY;
                *val = cpu_to_le32(tmp_val);
        }

        return count;
}

/* Test whether BARs match the value we think they should contain */
static bool vfio_need_bar_restore(struct vfio_pci_core_device *vdev)
{
        int i = 0, pos = PCI_BASE_ADDRESS_0, ret;
        u32 bar;

        for (; pos <= PCI_BASE_ADDRESS_5; i++, pos += 4) {
                if (vdev->rbar[i]) {
                        ret = pci_user_read_config_dword(vdev->pdev, pos, &bar);
                        if (ret || vdev->rbar[i] != bar)
                                return true;
                }
        }

        return false;
}

static int vfio_basic_config_write(struct vfio_pci_core_device *vdev, int pos,
                                   int count, struct perm_bits *perm,
                                   int offset, __le32 val)
{
        struct pci_dev *pdev = vdev->pdev;
        __le16 *virt_cmd;
        u16 new_cmd = 0;
        int ret;

        virt_cmd = (__le16 *)&vdev->vconfig[PCI_COMMAND];

        if (offset == PCI_COMMAND) {
                bool phys_mem, virt_mem, new_mem, phys_io, virt_io, new_io;
                u16 phys_cmd;

                ret = pci_user_read_config_word(pdev, PCI_COMMAND, &phys_cmd);
                if (ret)
                        return ret;

                new_cmd = le32_to_cpu(val);

                phys_io = !!(phys_cmd & PCI_COMMAND_IO);
                virt_io = !!(le16_to_cpu(*virt_cmd) & PCI_COMMAND_IO);
                new_io = !!(new_cmd & PCI_COMMAND_IO);

                phys_mem = !!(phys_cmd & PCI_COMMAND_MEMORY);
                virt_mem = !!(le16_to_cpu(*virt_cmd) & PCI_COMMAND_MEMORY);
                new_mem = !!(new_cmd & PCI_COMMAND_MEMORY);

                if (!new_mem) {
                        vfio_pci_zap_and_down_write_memory_lock(vdev);
                        vfio_pci_dma_buf_move(vdev, true);
                } else {
                        down_write(&vdev->memory_lock);
                }

                /*
                 * If the user is writing mem/io enable (new_mem/io) and we
                 * think it's already enabled (virt_mem/io), but the hardware
                 * shows it disabled (phys_mem/io, then the device has
                 * undergone some kind of backdoor reset and needs to be
                 * restored before we allow it to enable the bars.
                 * SR-IOV devices will trigger this - for mem enable let's
                 * catch this now and for io enable it will be caught later
                 */
                if ((new_mem && virt_mem && !phys_mem &&
                     !pdev->no_command_memory) ||
                    (new_io && virt_io && !phys_io) ||
                    vfio_need_bar_restore(vdev))
                        vfio_bar_restore(vdev);
        }

        count = vfio_default_config_write(vdev, pos, count, perm, offset, val);
        if (count < 0) {
                if (offset == PCI_COMMAND)
                        up_write(&vdev->memory_lock);
                return count;
        }

        /*
         * Save current memory/io enable bits in vconfig to allow for
         * the test above next time.
         */
        if (offset == PCI_COMMAND) {
                u16 mask = PCI_COMMAND_MEMORY | PCI_COMMAND_IO;

                *virt_cmd &= cpu_to_le16(~mask);
                *virt_cmd |= cpu_to_le16(new_cmd & mask);

                if (__vfio_pci_memory_enabled(vdev))
                        vfio_pci_dma_buf_move(vdev, false);
                up_write(&vdev->memory_lock);
        }

        /* Emulate INTx disable */
        if (offset >= PCI_COMMAND && offset <= PCI_COMMAND + 1) {
                bool virt_intx_disable;

                virt_intx_disable = !!(le16_to_cpu(*virt_cmd) &
                                       PCI_COMMAND_INTX_DISABLE);

                if (virt_intx_disable && !vdev->virq_disabled) {
                        vdev->virq_disabled = true;
                        vfio_pci_intx_mask(vdev);
                } else if (!virt_intx_disable && vdev->virq_disabled) {
                        vdev->virq_disabled = false;
                        vfio_pci_intx_unmask(vdev);
                }
        }

        if (is_bar(offset))
                vdev->bardirty = true;

        return count;
}

/* Permissions for the Basic PCI Header */
static int __init init_pci_cap_basic_perm(struct perm_bits *perm)
{
        if (alloc_perm_bits(perm, PCI_STD_HEADER_SIZEOF))
                return -ENOMEM;

        perm->readfn = vfio_basic_config_read;
        perm->writefn = vfio_basic_config_write;

        /* Virtualized for SR-IOV functions, which just have FFFF */
        p_setw(perm, PCI_VENDOR_ID, (u16)ALL_VIRT, NO_WRITE);
        p_setw(perm, PCI_DEVICE_ID, (u16)ALL_VIRT, NO_WRITE);

        /*
         * Virtualize INTx disable, we use it internally for interrupt
         * control and can emulate it for non-PCI 2.3 devices.
         */
        p_setw(perm, PCI_COMMAND, PCI_COMMAND_INTX_DISABLE, (u16)ALL_WRITE);

        /* Virtualize capability list, we might want to skip/disable */
        p_setw(perm, PCI_STATUS, PCI_STATUS_CAP_LIST, NO_WRITE);

        /* No harm to write */
        p_setb(perm, PCI_CACHE_LINE_SIZE, NO_VIRT, (u8)ALL_WRITE);
        p_setb(perm, PCI_LATENCY_TIMER, NO_VIRT, (u8)ALL_WRITE);
        p_setb(perm, PCI_BIST, NO_VIRT, (u8)ALL_WRITE);

        /* Virtualize all bars, can't touch the real ones */
        p_setd(perm, PCI_BASE_ADDRESS_0, ALL_VIRT, ALL_WRITE);
        p_setd(perm, PCI_BASE_ADDRESS_1, ALL_VIRT, ALL_WRITE);
        p_setd(perm, PCI_BASE_ADDRESS_2, ALL_VIRT, ALL_WRITE);
        p_setd(perm, PCI_BASE_ADDRESS_3, ALL_VIRT, ALL_WRITE);
        p_setd(perm, PCI_BASE_ADDRESS_4, ALL_VIRT, ALL_WRITE);
        p_setd(perm, PCI_BASE_ADDRESS_5, ALL_VIRT, ALL_WRITE);
        p_setd(perm, PCI_ROM_ADDRESS, ALL_VIRT, ALL_WRITE);

        /* Allow us to adjust capability chain */
        p_setb(perm, PCI_CAPABILITY_LIST, (u8)ALL_VIRT, NO_WRITE);

        /* Sometimes used by sw, just virtualize */
        p_setb(perm, PCI_INTERRUPT_LINE, (u8)ALL_VIRT, (u8)ALL_WRITE);

        /* Virtualize interrupt pin to allow hiding INTx */
        p_setb(perm, PCI_INTERRUPT_PIN, (u8)ALL_VIRT, (u8)NO_WRITE);

        return 0;
}

/*
 * It takes all the required locks to protect the access of power related
 * variables and then invokes vfio_pci_set_power_state().
 */
static void vfio_lock_and_set_power_state(struct vfio_pci_core_device *vdev,
                                          pci_power_t state)
{
        if (state >= PCI_D3hot) {
                vfio_pci_zap_and_down_write_memory_lock(vdev);
                vfio_pci_dma_buf_move(vdev, true);
        } else {
                down_write(&vdev->memory_lock);
        }

        vfio_pci_set_power_state(vdev, state);
        if (__vfio_pci_memory_enabled(vdev))
                vfio_pci_dma_buf_move(vdev, false);
        up_write(&vdev->memory_lock);
}

static int vfio_pm_config_write(struct vfio_pci_core_device *vdev, int pos,
                                int count, struct perm_bits *perm,
                                int offset, __le32 val)
{
        count = vfio_default_config_write(vdev, pos, count, perm, offset, val);
        if (count < 0)
                return count;

        if (offset == PCI_PM_CTRL) {
                pci_power_t state;

                switch (le32_to_cpu(val) & PCI_PM_CTRL_STATE_MASK) {
                case 0:
                        state = PCI_D0;
                        break;
                case 1:
                        state = PCI_D1;
                        break;
                case 2:
                        state = PCI_D2;
                        break;
                case 3:
                        state = PCI_D3hot;
                        break;
                }

                vfio_lock_and_set_power_state(vdev, state);
        }

        return count;
}

/* Permissions for the Power Management capability */
static int __init init_pci_cap_pm_perm(struct perm_bits *perm)
{
        if (alloc_perm_bits(perm, pci_cap_length[PCI_CAP_ID_PM]))
                return -ENOMEM;

        perm->writefn = vfio_pm_config_write;

        /*
         * We always virtualize the next field so we can remove
         * capabilities from the chain if we want to.
         */
        p_setb(perm, PCI_CAP_LIST_NEXT, (u8)ALL_VIRT, NO_WRITE);

        /*
         * The guests can't process PME events. If any PME event will be
         * generated, then it will be mostly handled in the host and the
         * host will clear the PME_STATUS. So virtualize PME_Support bits.
         * The vconfig bits will be cleared during device capability
         * initialization.
         */
        p_setw(perm, PCI_PM_PMC, PCI_PM_CAP_PME_MASK, NO_WRITE);

        /*
         * Power management is defined *per function*, so we can let
         * the user change power state, but we trap and initiate the
         * change ourselves, so the state bits are read-only.
         *
         * The guest can't process PME from D3cold so virtualize PME_Status
         * and PME_En bits. The vconfig bits will be cleared during device
         * capability initialization.
         */
        p_setd(perm, PCI_PM_CTRL,
               PCI_PM_CTRL_PME_ENABLE | PCI_PM_CTRL_PME_STATUS,
               ~(PCI_PM_CTRL_PME_ENABLE | PCI_PM_CTRL_PME_STATUS |
                 PCI_PM_CTRL_STATE_MASK));

        return 0;
}

static int vfio_vpd_config_write(struct vfio_pci_core_device *vdev, int pos,
                                 int count, struct perm_bits *perm,
                                 int offset, __le32 val)
{
        struct pci_dev *pdev = vdev->pdev;
        __le16 *paddr = (__le16 *)(vdev->vconfig + pos - offset + PCI_VPD_ADDR);
        __le32 *pdata = (__le32 *)(vdev->vconfig + pos - offset + PCI_VPD_DATA);
        u16 addr;
        u32 data;

        /*
         * Write through to emulation.  If the write includes the upper byte
         * of PCI_VPD_ADDR, then the PCI_VPD_ADDR_F bit is written and we
         * have work to do.
         */
        count = vfio_default_config_write(vdev, pos, count, perm, offset, val);
        if (count < 0 || offset > PCI_VPD_ADDR + 1 ||
            offset + count <= PCI_VPD_ADDR + 1)
                return count;

        addr = le16_to_cpu(*paddr);

        if (addr & PCI_VPD_ADDR_F) {
                data = le32_to_cpu(*pdata);
                if (pci_write_vpd(pdev, addr & ~PCI_VPD_ADDR_F, 4, &data) != 4)
                        return count;
        } else {
                data = 0;
                if (pci_read_vpd(pdev, addr, 4, &data) < 0)
                        return count;
                *pdata = cpu_to_le32(data);
        }

        /*
         * Toggle PCI_VPD_ADDR_F in the emulated PCI_VPD_ADDR register to
         * signal completion.  If an error occurs above, we assume that not
         * toggling this bit will induce a driver timeout.
         */
        addr ^= PCI_VPD_ADDR_F;
        *paddr = cpu_to_le16(addr);

        return count;
}

/* Permissions for Vital Product Data capability */
static int __init init_pci_cap_vpd_perm(struct perm_bits *perm)
{
        if (alloc_perm_bits(perm, pci_cap_length[PCI_CAP_ID_VPD]))
                return -ENOMEM;

        perm->writefn = vfio_vpd_config_write;

        /*
         * We always virtualize the next field so we can remove
         * capabilities from the chain if we want to.
         */
        p_setb(perm, PCI_CAP_LIST_NEXT, (u8)ALL_VIRT, NO_WRITE);

        /*
         * Both the address and data registers are virtualized to
         * enable access through the pci_vpd_read/write functions
         */
        p_setw(perm, PCI_VPD_ADDR, (u16)ALL_VIRT, (u16)ALL_WRITE);
        p_setd(perm, PCI_VPD_DATA, ALL_VIRT, ALL_WRITE);

        return 0;
}

/* Permissions for PCI-X capability */
static int __init init_pci_cap_pcix_perm(struct perm_bits *perm)
{
        /* Alloc 24, but only 8 are used in v0 */
        if (alloc_perm_bits(perm, PCI_CAP_PCIX_SIZEOF_V2))
                return -ENOMEM;

        p_setb(perm, PCI_CAP_LIST_NEXT, (u8)ALL_VIRT, NO_WRITE);

        p_setw(perm, PCI_X_CMD, NO_VIRT, (u16)ALL_WRITE);
        p_setd(perm, PCI_X_ECC_CSR, NO_VIRT, ALL_WRITE);
        return 0;
}

static int vfio_exp_config_write(struct vfio_pci_core_device *vdev, int pos,
                                 int count, struct perm_bits *perm,
                                 int offset, __le32 val)
{
        __le16 *ctrl = (__le16 *)(vdev->vconfig + pos -
                                  offset + PCI_EXP_DEVCTL);
        int readrq = le16_to_cpu(*ctrl) & PCI_EXP_DEVCTL_READRQ;

        count = vfio_default_config_write(vdev, pos, count, perm, offset, val);
        if (count < 0)
                return count;

        /*
         * The FLR bit is virtualized, if set and the device supports PCIe
         * FLR, issue a reset_function.  Regardless, clear the bit, the spec
         * requires it to be always read as zero.  NB, reset_function might
         * not use a PCIe FLR, we don't have that level of granularity.
         */
        if (*ctrl & cpu_to_le16(PCI_EXP_DEVCTL_BCR_FLR)) {
                u32 cap;
                int ret;

                *ctrl &= ~cpu_to_le16(PCI_EXP_DEVCTL_BCR_FLR);

                ret = pci_user_read_config_dword(vdev->pdev,
                                                 pos - offset + PCI_EXP_DEVCAP,
                                                 &cap);

                if (!ret && (cap & PCI_EXP_DEVCAP_FLR)) {
                        vfio_pci_zap_and_down_write_memory_lock(vdev);
                        vfio_pci_dma_buf_move(vdev, true);
                        pci_try_reset_function(vdev->pdev);
                        if (__vfio_pci_memory_enabled(vdev))
                                vfio_pci_dma_buf_move(vdev, false);
                        up_write(&vdev->memory_lock);
                }
        }

        /*
         * MPS is virtualized to the user, writes do not change the physical
         * register since determining a proper MPS value requires a system wide
         * device view.  The MRRS is largely independent of MPS, but since the
         * user does not have that system-wide view, they might set a safe, but
         * inefficiently low value.  Here we allow writes through to hardware,
         * but we set the floor to the physical device MPS setting, so that
         * we can at least use full TLPs, as defined by the MPS value.
         *
         * NB, if any devices actually depend on an artificially low MRRS
         * setting, this will need to be revisited, perhaps with a quirk
         * though pcie_set_readrq().
         */
        if (readrq != (le16_to_cpu(*ctrl) & PCI_EXP_DEVCTL_READRQ)) {
                readrq = 128 <<
                        ((le16_to_cpu(*ctrl) & PCI_EXP_DEVCTL_READRQ) >> 12);
                readrq = max(readrq, pcie_get_mps(vdev->pdev));

                pcie_set_readrq(vdev->pdev, readrq);
        }

        return count;
}

/* Permissions for PCI Express capability */
static int __init init_pci_cap_exp_perm(struct perm_bits *perm)
{
        /* Alloc largest of possible sizes */
        if (alloc_perm_bits(perm, PCI_CAP_EXP_ENDPOINT_SIZEOF_V2))
                return -ENOMEM;

        perm->writefn = vfio_exp_config_write;

        p_setb(perm, PCI_CAP_LIST_NEXT, (u8)ALL_VIRT, NO_WRITE);

        /*
         * Allow writes to device control fields, except devctl_phantom,
         * which could confuse IOMMU, MPS, which can break communication
         * with other physical devices, and the ARI bit in devctl2, which
         * is set at probe time.  FLR and MRRS get virtualized via our
         * writefn.
         */
        p_setw(perm, PCI_EXP_DEVCTL,
               PCI_EXP_DEVCTL_BCR_FLR | PCI_EXP_DEVCTL_PAYLOAD |
               PCI_EXP_DEVCTL_READRQ, ~PCI_EXP_DEVCTL_PHANTOM);
        p_setw(perm, PCI_EXP_DEVCTL2, NO_VIRT, ~PCI_EXP_DEVCTL2_ARI);
        return 0;
}

static int vfio_af_config_write(struct vfio_pci_core_device *vdev, int pos,
                                int count, struct perm_bits *perm,
                                int offset, __le32 val)
{
        u8 *ctrl = vdev->vconfig + pos - offset + PCI_AF_CTRL;

        count = vfio_default_config_write(vdev, pos, count, perm, offset, val);
        if (count < 0)
                return count;

        /*
         * The FLR bit is virtualized, if set and the device supports AF
         * FLR, issue a reset_function.  Regardless, clear the bit, the spec
         * requires it to be always read as zero.  NB, reset_function might
         * not use an AF FLR, we don't have that level of granularity.
         */
        if (*ctrl & PCI_AF_CTRL_FLR) {
                u8 cap;
                int ret;

                *ctrl &= ~PCI_AF_CTRL_FLR;

                ret = pci_user_read_config_byte(vdev->pdev,
                                                pos - offset + PCI_AF_CAP,
                                                &cap);

                if (!ret && (cap & PCI_AF_CAP_FLR) && (cap & PCI_AF_CAP_TP)) {
                        vfio_pci_zap_and_down_write_memory_lock(vdev);
                        vfio_pci_dma_buf_move(vdev, true);
                        pci_try_reset_function(vdev->pdev);
                        if (__vfio_pci_memory_enabled(vdev))
                                vfio_pci_dma_buf_move(vdev, false);
                        up_write(&vdev->memory_lock);
                }
        }

        return count;
}

/* Permissions for Advanced Function capability */
static int __init init_pci_cap_af_perm(struct perm_bits *perm)
{
        if (alloc_perm_bits(perm, pci_cap_length[PCI_CAP_ID_AF]))
                return -ENOMEM;

        perm->writefn = vfio_af_config_write;

        p_setb(perm, PCI_CAP_LIST_NEXT, (u8)ALL_VIRT, NO_WRITE);
        p_setb(perm, PCI_AF_CTRL, PCI_AF_CTRL_FLR, PCI_AF_CTRL_FLR);
        return 0;
}

/* Permissions for Advanced Error Reporting extended capability */
static int __init init_pci_ext_cap_err_perm(struct perm_bits *perm)
{
        u32 mask;

        if (alloc_perm_bits(perm, pci_ext_cap_length[PCI_EXT_CAP_ID_ERR]))
                return -ENOMEM;

        /*
         * Virtualize the first dword of all express capabilities
         * because it includes the next pointer.  This lets us later
         * remove capabilities from the chain if we need to.
         */
        p_setd(perm, 0, ALL_VIRT, NO_WRITE);

        /* Writable bits mask */
        mask =  PCI_ERR_UNC_UND |               /* Undefined */
                PCI_ERR_UNC_DLP |               /* Data Link Protocol */
                PCI_ERR_UNC_SURPDN |            /* Surprise Down */
                PCI_ERR_UNC_POISON_TLP |        /* Poisoned TLP */
                PCI_ERR_UNC_FCP |               /* Flow Control Protocol */
                PCI_ERR_UNC_COMP_TIME |         /* Completion Timeout */
                PCI_ERR_UNC_COMP_ABORT |        /* Completer Abort */
                PCI_ERR_UNC_UNX_COMP |          /* Unexpected Completion */
                PCI_ERR_UNC_RX_OVER |           /* Receiver Overflow */
                PCI_ERR_UNC_MALF_TLP |          /* Malformed TLP */
                PCI_ERR_UNC_ECRC |              /* ECRC Error Status */
                PCI_ERR_UNC_UNSUP |             /* Unsupported Request */
                PCI_ERR_UNC_ACSV |              /* ACS Violation */
                PCI_ERR_UNC_INTN |              /* internal error */
                PCI_ERR_UNC_MCBTLP |            /* MC blocked TLP */
                PCI_ERR_UNC_ATOMEG |            /* Atomic egress blocked */
                PCI_ERR_UNC_TLPPRE;             /* TLP prefix blocked */
        p_setd(perm, PCI_ERR_UNCOR_STATUS, NO_VIRT, mask);
        p_setd(perm, PCI_ERR_UNCOR_MASK, NO_VIRT, mask);
        p_setd(perm, PCI_ERR_UNCOR_SEVER, NO_VIRT, mask);

        mask =  PCI_ERR_COR_RCVR |              /* Receiver Error Status */
                PCI_ERR_COR_BAD_TLP |           /* Bad TLP Status */
                PCI_ERR_COR_BAD_DLLP |          /* Bad DLLP Status */
                PCI_ERR_COR_REP_ROLL |          /* REPLAY_NUM Rollover */
                PCI_ERR_COR_REP_TIMER |         /* Replay Timer Timeout */
                PCI_ERR_COR_ADV_NFAT |          /* Advisory Non-Fatal */
                PCI_ERR_COR_INTERNAL |          /* Corrected Internal */
                PCI_ERR_COR_LOG_OVER;           /* Header Log Overflow */
        p_setd(perm, PCI_ERR_COR_STATUS, NO_VIRT, mask);
        p_setd(perm, PCI_ERR_COR_MASK, NO_VIRT, mask);

        mask =  PCI_ERR_CAP_ECRC_GENE |         /* ECRC Generation Enable */
                PCI_ERR_CAP_ECRC_CHKE;          /* ECRC Check Enable */
        p_setd(perm, PCI_ERR_CAP, NO_VIRT, mask);
        return 0;
}

/* Permissions for Power Budgeting extended capability */
static int __init init_pci_ext_cap_pwr_perm(struct perm_bits *perm)
{
        if (alloc_perm_bits(perm, pci_ext_cap_length[PCI_EXT_CAP_ID_PWR]))
                return -ENOMEM;

        p_setd(perm, 0, ALL_VIRT, NO_WRITE);

        /* Writing the data selector is OK, the info is still read-only */
        p_setb(perm, PCI_PWR_DATA, NO_VIRT, (u8)ALL_WRITE);
        return 0;
}

/*
 * Initialize the shared permission tables
 */
void vfio_pci_uninit_perm_bits(void)
{
        free_perm_bits(&cap_perms[PCI_CAP_ID_BASIC]);

        free_perm_bits(&cap_perms[PCI_CAP_ID_PM]);
        free_perm_bits(&cap_perms[PCI_CAP_ID_VPD]);
        free_perm_bits(&cap_perms[PCI_CAP_ID_PCIX]);
        free_perm_bits(&cap_perms[PCI_CAP_ID_EXP]);
        free_perm_bits(&cap_perms[PCI_CAP_ID_AF]);

        free_perm_bits(&ecap_perms[PCI_EXT_CAP_ID_ERR]);
        free_perm_bits(&ecap_perms[PCI_EXT_CAP_ID_PWR]);
}

int __init vfio_pci_init_perm_bits(void)
{
        int ret;

        /* Basic config space */
        ret = init_pci_cap_basic_perm(&cap_perms[PCI_CAP_ID_BASIC]);

        /* Capabilities */
        ret |= init_pci_cap_pm_perm(&cap_perms[PCI_CAP_ID_PM]);
        ret |= init_pci_cap_vpd_perm(&cap_perms[PCI_CAP_ID_VPD]);
        ret |= init_pci_cap_pcix_perm(&cap_perms[PCI_CAP_ID_PCIX]);
        cap_perms[PCI_CAP_ID_VNDR].writefn = vfio_raw_config_write;
        ret |= init_pci_cap_exp_perm(&cap_perms[PCI_CAP_ID_EXP]);
        ret |= init_pci_cap_af_perm(&cap_perms[PCI_CAP_ID_AF]);

        /* Extended capabilities */
        ret |= init_pci_ext_cap_err_perm(&ecap_perms[PCI_EXT_CAP_ID_ERR]);
        ret |= init_pci_ext_cap_pwr_perm(&ecap_perms[PCI_EXT_CAP_ID_PWR]);
        ecap_perms[PCI_EXT_CAP_ID_VNDR].writefn = vfio_raw_config_write;
        ecap_perms[PCI_EXT_CAP_ID_DVSEC].writefn = vfio_raw_config_write;

        if (ret)
                vfio_pci_uninit_perm_bits();

        return ret;
}

static int vfio_find_cap_start(struct vfio_pci_core_device *vdev, int pos)
{
        u8 cap;
        int base = (pos >= PCI_CFG_SPACE_SIZE) ? PCI_CFG_SPACE_SIZE :
                                                 PCI_STD_HEADER_SIZEOF;
        cap = vdev->pci_config_map[pos];

        if (cap == PCI_CAP_ID_BASIC)
                return 0;

        /* XXX Can we have to abutting capabilities of the same type? */
        while (pos - 1 >= base && vdev->pci_config_map[pos - 1] == cap)
                pos--;

        return pos;
}

static int vfio_msi_config_read(struct vfio_pci_core_device *vdev, int pos,
                                int count, struct perm_bits *perm,
                                int offset, __le32 *val)
{
        /* Update max available queue size from msi_qmax */
        if (offset <= PCI_MSI_FLAGS && offset + count >= PCI_MSI_FLAGS) {
                __le16 *flags;
                int start;

                start = vfio_find_cap_start(vdev, pos);

                flags = (__le16 *)&vdev->vconfig[start];

                *flags &= cpu_to_le16(~PCI_MSI_FLAGS_QMASK);
                *flags |= cpu_to_le16(vdev->msi_qmax << 1);
        }

        return vfio_default_config_read(vdev, pos, count, perm, offset, val);
}

static int vfio_msi_config_write(struct vfio_pci_core_device *vdev, int pos,
                                 int count, struct perm_bits *perm,
                                 int offset, __le32 val)
{
        count = vfio_default_config_write(vdev, pos, count, perm, offset, val);
        if (count < 0)
                return count;

        /* Fixup and write configured queue size and enable to hardware */
        if (offset <= PCI_MSI_FLAGS && offset + count >= PCI_MSI_FLAGS) {
                __le16 *pflags;
                u16 flags;
                int start, ret;

                start = vfio_find_cap_start(vdev, pos);

                pflags = (__le16 *)&vdev->vconfig[start + PCI_MSI_FLAGS];

                flags = le16_to_cpu(*pflags);

                /* MSI is enabled via ioctl */
                if  (vdev->irq_type != VFIO_PCI_MSI_IRQ_INDEX)
                        flags &= ~PCI_MSI_FLAGS_ENABLE;

                /* Check queue size */
                if ((flags & PCI_MSI_FLAGS_QSIZE) >> 4 > vdev->msi_qmax) {
                        flags &= ~PCI_MSI_FLAGS_QSIZE;
                        flags |= vdev->msi_qmax << 4;
                }

                /* Write back to virt and to hardware */
                *pflags = cpu_to_le16(flags);
                ret = pci_user_write_config_word(vdev->pdev,
                                                 start + PCI_MSI_FLAGS,
                                                 flags);
                if (ret)
                        return ret;
        }

        return count;
}

/*
 * MSI determination is per-device, so this routine gets used beyond
 * initialization time. Don't add __init
 */
static int init_pci_cap_msi_perm(struct perm_bits *perm, int len, u16 flags)
{
        if (alloc_perm_bits(perm, len))
                return -ENOMEM;

        perm->readfn = vfio_msi_config_read;
        perm->writefn = vfio_msi_config_write;

        p_setb(perm, PCI_CAP_LIST_NEXT, (u8)ALL_VIRT, NO_WRITE);

        /*
         * The upper byte of the control register is reserved,
         * just setup the lower byte.
         */
        p_setb(perm, PCI_MSI_FLAGS, (u8)ALL_VIRT, (u8)ALL_WRITE);
        p_setd(perm, PCI_MSI_ADDRESS_LO, ALL_VIRT, ALL_WRITE);
        if (flags & PCI_MSI_FLAGS_64BIT) {
                p_setd(perm, PCI_MSI_ADDRESS_HI, ALL_VIRT, ALL_WRITE);
                p_setw(perm, PCI_MSI_DATA_64, (u16)ALL_VIRT, (u16)ALL_WRITE);
                if (flags & PCI_MSI_FLAGS_MASKBIT) {
                        p_setd(perm, PCI_MSI_MASK_64, NO_VIRT, ALL_WRITE);
                        p_setd(perm, PCI_MSI_PENDING_64, NO_VIRT, ALL_WRITE);
                }
        } else {
                p_setw(perm, PCI_MSI_DATA_32, (u16)ALL_VIRT, (u16)ALL_WRITE);
                if (flags & PCI_MSI_FLAGS_MASKBIT) {
                        p_setd(perm, PCI_MSI_MASK_32, NO_VIRT, ALL_WRITE);
                        p_setd(perm, PCI_MSI_PENDING_32, NO_VIRT, ALL_WRITE);
                }
        }
        return 0;
}

/* Determine MSI CAP field length; initialize msi_perms on 1st call per vdev */
static int vfio_msi_cap_len(struct vfio_pci_core_device *vdev, u8 pos)
{
        struct pci_dev *pdev = vdev->pdev;
        int len, ret;
        u16 flags;

        ret = pci_read_config_word(pdev, pos + PCI_MSI_FLAGS, &flags);
        if (ret)
                return pcibios_err_to_errno(ret);

        len = 10; /* Minimum size */
        if (flags & PCI_MSI_FLAGS_64BIT)
                len += 4;
        if (flags & PCI_MSI_FLAGS_MASKBIT)
                len += 10;

        if (vdev->msi_perm)
                return len;

        vdev->msi_perm = kmalloc_obj(struct perm_bits, GFP_KERNEL_ACCOUNT);
        if (!vdev->msi_perm)
                return -ENOMEM;

        ret = init_pci_cap_msi_perm(vdev->msi_perm, len, flags);
        if (ret) {
                kfree(vdev->msi_perm);
                return ret;
        }

        return len;
}

/* Determine extended capability length for VC (2 & 9) and MFVC */
static int vfio_vc_cap_len(struct vfio_pci_core_device *vdev, u16 pos)
{
        struct pci_dev *pdev = vdev->pdev;
        u32 tmp;
        int ret, evcc, phases, vc_arb;
        int len = PCI_CAP_VC_BASE_SIZEOF;

        ret = pci_read_config_dword(pdev, pos + PCI_VC_PORT_CAP1, &tmp);
        if (ret)
                return pcibios_err_to_errno(ret);

        evcc = tmp & PCI_VC_CAP1_EVCC; /* extended vc count */
        ret = pci_read_config_dword(pdev, pos + PCI_VC_PORT_CAP2, &tmp);
        if (ret)
                return pcibios_err_to_errno(ret);

        if (tmp & PCI_VC_CAP2_128_PHASE)
                phases = 128;
        else if (tmp & PCI_VC_CAP2_64_PHASE)
                phases = 64;
        else if (tmp & PCI_VC_CAP2_32_PHASE)
                phases = 32;
        else
                phases = 0;

        vc_arb = phases * 4;

        /*
         * Port arbitration tables are root & switch only;
         * function arbitration tables are function 0 only.
         * In either case, we'll never let user write them so
         * we don't care how big they are
         */
        len += (1 + evcc) * PCI_CAP_VC_PER_VC_SIZEOF;
        if (vc_arb) {
                len = round_up(len, 16);
                len += vc_arb / 8;
        }
        return len;
}

static int vfio_cap_len(struct vfio_pci_core_device *vdev, u8 cap, u8 pos)
{
        struct pci_dev *pdev = vdev->pdev;
        u32 dword;
        u16 word;
        u8 byte;
        int ret;

        switch (cap) {
        case PCI_CAP_ID_MSI:
                return vfio_msi_cap_len(vdev, pos);
        case PCI_CAP_ID_PCIX:
                ret = pci_read_config_word(pdev, pos + PCI_X_CMD, &word);
                if (ret)
                        return pcibios_err_to_errno(ret);

                if (PCI_X_CMD_VERSION(word)) {
                        if (pdev->cfg_size > PCI_CFG_SPACE_SIZE) {
                                /* Test for extended capabilities */
                                pci_read_config_dword(pdev, PCI_CFG_SPACE_SIZE,
                                                      &dword);
                                vdev->extended_caps = (dword != 0);
                        }
                        return PCI_CAP_PCIX_SIZEOF_V2;
                } else
                        return PCI_CAP_PCIX_SIZEOF_V0;
        case PCI_CAP_ID_VNDR:
                /* length follows next field */
                ret = pci_read_config_byte(pdev, pos + PCI_CAP_FLAGS, &byte);
                if (ret)
                        return pcibios_err_to_errno(ret);

                return byte;
        case PCI_CAP_ID_EXP:
                if (pdev->cfg_size > PCI_CFG_SPACE_SIZE) {
                        /* Test for extended capabilities */
                        pci_read_config_dword(pdev, PCI_CFG_SPACE_SIZE, &dword);
                        vdev->extended_caps = (dword != 0);
                }

                /* length based on version and type */
                if ((pcie_caps_reg(pdev) & PCI_EXP_FLAGS_VERS) == 1) {
                        if (pci_pcie_type(pdev) == PCI_EXP_TYPE_RC_END)
                                return 0xc; /* "All Devices" only, no link */
                        return PCI_CAP_EXP_ENDPOINT_SIZEOF_V1;
                } else {
                        if (pci_pcie_type(pdev) == PCI_EXP_TYPE_RC_END)
                                return 0x2c; /* No link */
                        return PCI_CAP_EXP_ENDPOINT_SIZEOF_V2;
                }
        case PCI_CAP_ID_HT:
                ret = pci_read_config_byte(pdev, pos + 3, &byte);
                if (ret)
                        return pcibios_err_to_errno(ret);

                return (byte & HT_3BIT_CAP_MASK) ?
                        HT_CAP_SIZEOF_SHORT : HT_CAP_SIZEOF_LONG;
        case PCI_CAP_ID_SATA:
                ret = pci_read_config_byte(pdev, pos + PCI_SATA_REGS, &byte);
                if (ret)
                        return pcibios_err_to_errno(ret);

                byte &= PCI_SATA_REGS_MASK;
                if (byte == PCI_SATA_REGS_INLINE)
                        return PCI_SATA_SIZEOF_LONG;
                else
                        return PCI_SATA_SIZEOF_SHORT;
        default:
                pci_warn(pdev, "%s: unknown length for PCI cap %#x@%#x\n",
                         __func__, cap, pos);
        }

        return 0;
}

static int vfio_ext_cap_len(struct vfio_pci_core_device *vdev, u16 ecap, u16 epos)
{
        struct pci_dev *pdev = vdev->pdev;
        u8 byte;
        u32 dword;
        int ret;

        switch (ecap) {
        case PCI_EXT_CAP_ID_VNDR:
                ret = pci_read_config_dword(pdev, epos + PCI_VNDR_HEADER,
                                            &dword);
                if (ret)
                        return pcibios_err_to_errno(ret);

                return PCI_VNDR_HEADER_LEN(dword);
        case PCI_EXT_CAP_ID_VC:
        case PCI_EXT_CAP_ID_VC9:
        case PCI_EXT_CAP_ID_MFVC:
                return vfio_vc_cap_len(vdev, epos);
        case PCI_EXT_CAP_ID_ACS:
                ret = pci_read_config_byte(pdev, epos + PCI_ACS_CAP, &byte);
                if (ret)
                        return pcibios_err_to_errno(ret);

                if (byte & PCI_ACS_EC) {
                        int bits;

                        ret = pci_read_config_byte(pdev,
                                                   epos + PCI_ACS_EGRESS_BITS,
                                                   &byte);
                        if (ret)
                                return pcibios_err_to_errno(ret);

                        bits = byte ? round_up(byte, 32) : 256;
                        return 8 + (bits / 8);
                }
                return 8;

        case PCI_EXT_CAP_ID_REBAR:
                ret = pci_read_config_byte(pdev, epos + PCI_REBAR_CTRL, &byte);
                if (ret)
                        return pcibios_err_to_errno(ret);

                byte &= PCI_REBAR_CTRL_NBAR_MASK;
                byte >>= PCI_REBAR_CTRL_NBAR_SHIFT;

                return 4 + (byte * 8);
        case PCI_EXT_CAP_ID_DPA:
                ret = pci_read_config_byte(pdev, epos + PCI_DPA_CAP, &byte);
                if (ret)
                        return pcibios_err_to_errno(ret);

                byte &= PCI_DPA_CAP_SUBSTATE_MASK;
                return PCI_DPA_BASE_SIZEOF + byte + 1;
        case PCI_EXT_CAP_ID_TPH:
                ret = pci_read_config_dword(pdev, epos + PCI_TPH_CAP, &dword);
                if (ret)
                        return pcibios_err_to_errno(ret);

                if ((dword & PCI_TPH_CAP_LOC_MASK) == PCI_TPH_LOC_CAP) {
                        int sts;

                        sts = dword & PCI_TPH_CAP_ST_MASK;
                        sts >>= PCI_TPH_CAP_ST_SHIFT;
                        return PCI_TPH_BASE_SIZEOF + (sts * 2) + 2;
                }
                return PCI_TPH_BASE_SIZEOF;
        case PCI_EXT_CAP_ID_DVSEC:
                ret = pci_read_config_dword(pdev, epos + PCI_DVSEC_HEADER1, &dword);
                if (ret)
                        return pcibios_err_to_errno(ret);
                return PCI_DVSEC_HEADER1_LEN(dword);
        default:
                pci_warn(pdev, "%s: unknown length for PCI ecap %#x@%#x\n",
                         __func__, ecap, epos);
        }

        return 0;
}

static void vfio_update_pm_vconfig_bytes(struct vfio_pci_core_device *vdev,
                                         int offset)
{
        __le16 *pmc = (__le16 *)&vdev->vconfig[offset + PCI_PM_PMC];
        __le16 *ctrl = (__le16 *)&vdev->vconfig[offset + PCI_PM_CTRL];

        /* Clear vconfig PME_Support, PME_Status, and PME_En bits */
        *pmc &= ~cpu_to_le16(PCI_PM_CAP_PME_MASK);
        *ctrl &= ~cpu_to_le16(PCI_PM_CTRL_PME_ENABLE | PCI_PM_CTRL_PME_STATUS);
}

static int vfio_fill_vconfig_bytes(struct vfio_pci_core_device *vdev,
                                   int offset, int size)
{
        struct pci_dev *pdev = vdev->pdev;
        int ret = 0;

        /*
         * We try to read physical config space in the largest chunks
         * we can, assuming that all of the fields support dword access.
         * pci_save_state() makes this same assumption and seems to do ok.
         */
        while (size) {
                int filled;

                if (size >= 4 && !(offset % 4)) {
                        __le32 *dwordp = (__le32 *)&vdev->vconfig[offset];
                        u32 dword;

                        ret = pci_read_config_dword(pdev, offset, &dword);
                        if (ret)
                                return ret;
                        *dwordp = cpu_to_le32(dword);
                        filled = 4;
                } else if (size >= 2 && !(offset % 2)) {
                        __le16 *wordp = (__le16 *)&vdev->vconfig[offset];
                        u16 word;

                        ret = pci_read_config_word(pdev, offset, &word);
                        if (ret)
                                return ret;
                        *wordp = cpu_to_le16(word);
                        filled = 2;
                } else {
                        u8 *byte = &vdev->vconfig[offset];
                        ret = pci_read_config_byte(pdev, offset, byte);
                        if (ret)
                                return ret;
                        filled = 1;
                }

                offset += filled;
                size -= filled;
        }

        return ret;
}

static int vfio_cap_init(struct vfio_pci_core_device *vdev)
{
        struct pci_dev *pdev = vdev->pdev;
        u8 *map = vdev->pci_config_map;
        u16 status;
        u8 pos, *prev, cap;
        int loops, ret, caps = 0;

        /* Any capabilities? */
        ret = pci_read_config_word(pdev, PCI_STATUS, &status);
        if (ret)
                return ret;

        if (!(status & PCI_STATUS_CAP_LIST))
                return 0; /* Done */

        ret = pci_read_config_byte(pdev, PCI_CAPABILITY_LIST, &pos);
        if (ret)
                return ret;

        /* Mark the previous position in case we want to skip a capability */
        prev = &vdev->vconfig[PCI_CAPABILITY_LIST];

        /* We can bound our loop, capabilities are dword aligned */
        loops = (PCI_CFG_SPACE_SIZE - PCI_STD_HEADER_SIZEOF) / PCI_CAP_SIZEOF;
        while (pos && loops--) {
                u8 next;
                int i, len = 0;

                ret = pci_read_config_byte(pdev, pos, &cap);
                if (ret)
                        return ret;

                ret = pci_read_config_byte(pdev,
                                           pos + PCI_CAP_LIST_NEXT, &next);
                if (ret)
                        return ret;

                /*
                 * ID 0 is a NULL capability, conflicting with our fake
                 * PCI_CAP_ID_BASIC.  As it has no content, consider it
                 * hidden for now.
                 */
                if (cap && cap <= PCI_CAP_ID_MAX) {
                        len = pci_cap_length[cap];
                        if (len == 0xFF) { /* Variable length */
                                len = vfio_cap_len(vdev, cap, pos);
                                if (len < 0)
                                        return len;
                        }
                }

                if (!len) {
                        pci_dbg(pdev, "%s: hiding cap %#x@%#x\n", __func__,
                                cap, pos);
                        *prev = next;
                        pos = next;
                        continue;
                }

                /* Sanity check, do we overlap other capabilities? */
                for (i = 0; i < len; i++) {
                        if (likely(map[pos + i] == PCI_CAP_ID_INVALID))
                                continue;

                        pci_warn(pdev, "%s: PCI config conflict @%#x, was cap %#x now cap %#x\n",
                                 __func__, pos + i, map[pos + i], cap);
                }

                BUILD_BUG_ON(PCI_CAP_ID_MAX >= PCI_CAP_ID_INVALID_VIRT);

                memset(map + pos, cap, len);
                ret = vfio_fill_vconfig_bytes(vdev, pos, len);
                if (ret)
                        return ret;

                if (cap == PCI_CAP_ID_PM)
                        vfio_update_pm_vconfig_bytes(vdev, pos);

                prev = &vdev->vconfig[pos + PCI_CAP_LIST_NEXT];
                pos = next;
                caps++;
        }

        /* If we didn't fill any capabilities, clear the status flag */
        if (!caps) {
                __le16 *vstatus = (__le16 *)&vdev->vconfig[PCI_STATUS];
                *vstatus &= ~cpu_to_le16(PCI_STATUS_CAP_LIST);
        }

        return 0;
}

static int vfio_ecap_init(struct vfio_pci_core_device *vdev)
{
        struct pci_dev *pdev = vdev->pdev;
        u8 *map = vdev->pci_config_map;
        u16 epos;
        __le32 *prev = NULL;
        int loops, ret, ecaps = 0;

        if (!vdev->extended_caps)
                return 0;

        epos = PCI_CFG_SPACE_SIZE;

        loops = (pdev->cfg_size - PCI_CFG_SPACE_SIZE) / PCI_CAP_SIZEOF;

        while (loops-- && epos >= PCI_CFG_SPACE_SIZE) {
                u32 header;
                u16 ecap;
                int i, len = 0;
                bool hidden = false;

                ret = pci_read_config_dword(pdev, epos, &header);
                if (ret)
                        return ret;

                ecap = PCI_EXT_CAP_ID(header);

                if (ecap <= PCI_EXT_CAP_ID_MAX) {
                        len = pci_ext_cap_length[ecap];
                        if (len == 0xFF) {
                                len = vfio_ext_cap_len(vdev, ecap, epos);
                                if (len < 0)
                                        return len;
                        }
                }

                if (!len) {
                        pci_dbg(pdev, "%s: hiding ecap %#x@%#x\n",
                                __func__, ecap, epos);

                        /* If not the first in the chain, we can skip over it */
                        if (prev) {
                                u32 val = epos = PCI_EXT_CAP_NEXT(header);
                                *prev &= cpu_to_le32(~(0xffcU << 20));
                                *prev |= cpu_to_le32(val << 20);
                                continue;
                        }

                        /*
                         * Otherwise, fill in a placeholder, the direct
                         * readfn will virtualize this automatically
                         */
                        len = PCI_CAP_SIZEOF;
                        hidden = true;
                }

                for (i = 0; i < len; i++) {
                        if (likely(map[epos + i] == PCI_CAP_ID_INVALID))
                                continue;

                        pci_warn(pdev, "%s: PCI config conflict @%#x, was ecap %#x now ecap %#x\n",
                                 __func__, epos + i, map[epos + i], ecap);
                }

                /*
                 * Even though ecap is 2 bytes, we're currently a long way
                 * from exceeding 1 byte capabilities.  If we ever make it
                 * up to 0xFE we'll need to up this to a two-byte, byte map.
                 */
                BUILD_BUG_ON(PCI_EXT_CAP_ID_MAX >= PCI_CAP_ID_INVALID_VIRT);

                memset(map + epos, ecap, len);
                ret = vfio_fill_vconfig_bytes(vdev, epos, len);
                if (ret)
                        return ret;

                /*
                 * If we're just using this capability to anchor the list,
                 * hide the real ID.  Only count real ecaps.  XXX PCI spec
                 * indicates to use cap id = 0, version = 0, next = 0 if
                 * ecaps are absent, hope users check all the way to next.
                 */
                if (hidden)
                        *(__le32 *)&vdev->vconfig[epos] &=
                                cpu_to_le32((0xffcU << 20));
                else
                        ecaps++;

                prev = (__le32 *)&vdev->vconfig[epos];
                epos = PCI_EXT_CAP_NEXT(header);
        }

        if (!ecaps)
                *(u32 *)&vdev->vconfig[PCI_CFG_SPACE_SIZE] = 0;

        return 0;
}

/*
 * Nag about hardware bugs, hopefully to have vendors fix them, but at least
 * to collect a list of dependencies for the VF INTx pin quirk below.
 */
static const struct pci_device_id known_bogus_vf_intx_pin[] = {
        { PCI_DEVICE(PCI_VENDOR_ID_INTEL, 0x270c) },
        {}
};

/*
 * For each device we allocate a pci_config_map that indicates the
 * capability occupying each dword and thus the struct perm_bits we
 * use for read and write.  We also allocate a virtualized config
 * space which tracks reads and writes to bits that we emulate for
 * the user.  Initial values filled from device.
 *
 * Using shared struct perm_bits between all vfio-pci devices saves
 * us from allocating cfg_size buffers for virt and write for every
 * device.  We could remove vconfig and allocate individual buffers
 * for each area requiring emulated bits, but the array of pointers
 * would be comparable in size (at least for standard config space).
 */
int vfio_config_init(struct vfio_pci_core_device *vdev)
{
        struct pci_dev *pdev = vdev->pdev;
        u8 *map, *vconfig;
        int ret;

        /*
         * Config space, caps and ecaps are all dword aligned, so we could
         * use one byte per dword to record the type.  However, there are
         * no requirements on the length of a capability, so the gap between
         * capabilities needs byte granularity.
         */
        map = kmalloc(pdev->cfg_size, GFP_KERNEL_ACCOUNT);
        if (!map)
                return -ENOMEM;

        vconfig = kmalloc(pdev->cfg_size, GFP_KERNEL_ACCOUNT);
        if (!vconfig) {
                kfree(map);
                return -ENOMEM;
        }

        vdev->pci_config_map = map;
        vdev->vconfig = vconfig;

        memset(map, PCI_CAP_ID_BASIC, PCI_STD_HEADER_SIZEOF);
        memset(map + PCI_STD_HEADER_SIZEOF, PCI_CAP_ID_INVALID,
               pdev->cfg_size - PCI_STD_HEADER_SIZEOF);

        ret = vfio_fill_vconfig_bytes(vdev, 0, PCI_STD_HEADER_SIZEOF);
        if (ret)
                goto out;

        vdev->bardirty = true;

        /*
         * XXX can we just pci_load_saved_state/pci_restore_state?
         * may need to rebuild vconfig after that
         */

        /* For restore after reset */
        vdev->rbar[0] = le32_to_cpu(*(__le32 *)&vconfig[PCI_BASE_ADDRESS_0]);
        vdev->rbar[1] = le32_to_cpu(*(__le32 *)&vconfig[PCI_BASE_ADDRESS_1]);
        vdev->rbar[2] = le32_to_cpu(*(__le32 *)&vconfig[PCI_BASE_ADDRESS_2]);
        vdev->rbar[3] = le32_to_cpu(*(__le32 *)&vconfig[PCI_BASE_ADDRESS_3]);
        vdev->rbar[4] = le32_to_cpu(*(__le32 *)&vconfig[PCI_BASE_ADDRESS_4]);
        vdev->rbar[5] = le32_to_cpu(*(__le32 *)&vconfig[PCI_BASE_ADDRESS_5]);
        vdev->rbar[6] = le32_to_cpu(*(__le32 *)&vconfig[PCI_ROM_ADDRESS]);

        if (pdev->is_virtfn) {
                *(__le16 *)&vconfig[PCI_VENDOR_ID] = cpu_to_le16(pdev->vendor);
                *(__le16 *)&vconfig[PCI_DEVICE_ID] = cpu_to_le16(pdev->device);

                /*
                 * Per SR-IOV spec rev 1.1, 3.4.1.18 the interrupt pin register
                 * does not apply to VFs and VFs must implement this register
                 * as read-only with value zero.  Userspace is not readily able
                 * to identify whether a device is a VF and thus that the pin
                 * definition on the device is bogus should it violate this
                 * requirement.  We already virtualize the pin register for
                 * other purposes, so we simply need to replace the bogus value
                 * and consider VFs when we determine INTx IRQ count.
                 */
                if (vconfig[PCI_INTERRUPT_PIN] &&
                    !pci_match_id(known_bogus_vf_intx_pin, pdev))
                        pci_warn(pdev,
                                 "Hardware bug: VF reports bogus INTx pin %d\n",
                                 vconfig[PCI_INTERRUPT_PIN]);

                vconfig[PCI_INTERRUPT_PIN] = 0; /* Gratuitous for good VFs */
        }
        if (pdev->no_command_memory) {
                /*
                 * VFs and devices that set pdev->no_command_memory do not
                 * implement the memory enable bit of the COMMAND register
                 * therefore we'll not have it set in our initial copy of
                 * config space after pci_enable_device().  For consistency
                 * with PFs, set the virtual enable bit here.
                 */
                *(__le16 *)&vconfig[PCI_COMMAND] |=
                                        cpu_to_le16(PCI_COMMAND_MEMORY);
        }

        if (!IS_ENABLED(CONFIG_VFIO_PCI_INTX) || vdev->nointx ||
            !vdev->pdev->irq || vdev->pdev->irq == IRQ_NOTCONNECTED)
                vconfig[PCI_INTERRUPT_PIN] = 0;

        ret = vfio_cap_init(vdev);
        if (ret)
                goto out;

        ret = vfio_ecap_init(vdev);
        if (ret)
                goto out;

        return 0;

out:
        kfree(map);
        vdev->pci_config_map = NULL;
        kfree(vconfig);
        vdev->vconfig = NULL;
        return pcibios_err_to_errno(ret);
}

void vfio_config_free(struct vfio_pci_core_device *vdev)
{
        kfree(vdev->vconfig);
        vdev->vconfig = NULL;
        kfree(vdev->pci_config_map);
        vdev->pci_config_map = NULL;
        if (vdev->msi_perm) {
                free_perm_bits(vdev->msi_perm);
                kfree(vdev->msi_perm);
                vdev->msi_perm = NULL;
        }
}

/*
 * Find the remaining number of bytes in a dword that match the given
 * position.  Stop at either the end of the capability or the dword boundary.
 */
static size_t vfio_pci_cap_remaining_dword(struct vfio_pci_core_device *vdev,
                                           loff_t pos)
{
        u8 cap = vdev->pci_config_map[pos];
        size_t i;

        for (i = 1; (pos + i) % 4 && vdev->pci_config_map[pos + i] == cap; i++)
                /* nop */;

        return i;
}

static ssize_t vfio_config_do_rw(struct vfio_pci_core_device *vdev, char __user *buf,
                                 size_t count, loff_t *ppos, bool iswrite)
{
        struct pci_dev *pdev = vdev->pdev;
        struct perm_bits *perm;
        __le32 val = 0;
        int cap_start = 0, offset;
        u8 cap_id;
        ssize_t ret;

        if (*ppos < 0 || *ppos >= pdev->cfg_size ||
            *ppos + count > pdev->cfg_size)
                return -EFAULT;

        /*
         * Chop accesses into aligned chunks containing no more than a
         * single capability.  Caller increments to the next chunk.
         */
        count = min(count, vfio_pci_cap_remaining_dword(vdev, *ppos));
        if (count >= 4 && !(*ppos % 4))
                count = 4;
        else if (count >= 2 && !(*ppos % 2))
                count = 2;
        else
                count = 1;

        ret = count;

        cap_id = vdev->pci_config_map[*ppos];

        if (cap_id == PCI_CAP_ID_INVALID) {
                perm = &unassigned_perms;
                cap_start = *ppos;
        } else if (cap_id == PCI_CAP_ID_INVALID_VIRT) {
                perm = &virt_perms;
                cap_start = *ppos;
        } else {
                if (*ppos >= PCI_CFG_SPACE_SIZE) {
                        /*
                         * We can get a cap_id that exceeds PCI_EXT_CAP_ID_MAX
                         * if we're hiding an unknown capability at the start
                         * of the extended capability list.  Use default, ro
                         * access, which will virtualize the id and next values.
                         */
                        if (cap_id > PCI_EXT_CAP_ID_MAX)
                                perm = &direct_ro_perms;
                        else
                                perm = &ecap_perms[cap_id];

                        cap_start = vfio_find_cap_start(vdev, *ppos);
                } else {
                        WARN_ON(cap_id > PCI_CAP_ID_MAX);

                        perm = &cap_perms[cap_id];

                        if (cap_id == PCI_CAP_ID_MSI)
                                perm = vdev->msi_perm;

                        if (cap_id > PCI_CAP_ID_BASIC)
                                cap_start = vfio_find_cap_start(vdev, *ppos);
                }
        }

        WARN_ON(!cap_start && cap_id != PCI_CAP_ID_BASIC);
        WARN_ON(cap_start > *ppos);

        offset = *ppos - cap_start;

        if (iswrite) {
                if (!perm->writefn)
                        return ret;

                if (copy_from_user(&val, buf, count))
                        return -EFAULT;

                ret = perm->writefn(vdev, *ppos, count, perm, offset, val);
        } else {
                if (perm->readfn) {
                        ret = perm->readfn(vdev, *ppos, count,
                                           perm, offset, &val);
                        if (ret < 0)
                                return ret;
                }

                if (copy_to_user(buf, &val, count))
                        return -EFAULT;
        }

        return ret;
}

ssize_t vfio_pci_config_rw(struct vfio_pci_core_device *vdev, char __user *buf,
                           size_t count, loff_t *ppos, bool iswrite)
{
        size_t done = 0;
        int ret = 0;
        loff_t pos = *ppos;

        pos &= VFIO_PCI_OFFSET_MASK;

        while (count) {
                ret = vfio_config_do_rw(vdev, buf, count, &pos, iswrite);
                if (ret < 0)
                        return ret;

                count -= ret;
                done += ret;
                buf += ret;
                pos += ret;
        }

        *ppos += done;

        return done;
}

/**
 * vfio_pci_core_range_intersect_range() - Determine overlap between a buffer
 *                                         and register offset ranges.
 * @buf_start:          start offset of the buffer
 * @buf_cnt:            number of buffer bytes
 * @reg_start:          start register offset
 * @reg_cnt:            number of register bytes
 * @buf_offset: start offset of overlap in the buffer
 * @intersect_count:    number of overlapping bytes
 * @register_offset:    start offset of overlap in register
 *
 * Returns: true if there is overlap, false if not.
 * The overlap start and size is returned through function args.
 */
bool vfio_pci_core_range_intersect_range(loff_t buf_start, size_t buf_cnt,
                                         loff_t reg_start, size_t reg_cnt,
                                         loff_t *buf_offset,
                                         size_t *intersect_count,
                                         size_t *register_offset)
{
        if (buf_start <= reg_start &&
            buf_start + buf_cnt > reg_start) {
                *buf_offset = reg_start - buf_start;
                *intersect_count = min_t(size_t, reg_cnt,
                                         buf_start + buf_cnt - reg_start);
                *register_offset = 0;
                return true;
        }

        if (buf_start > reg_start &&
            buf_start < reg_start + reg_cnt) {
                *buf_offset = 0;
                *intersect_count = min_t(size_t, buf_cnt,
                                         reg_start + reg_cnt - buf_start);
                *register_offset = buf_start - reg_start;
                return true;
        }

        return false;
}
EXPORT_SYMBOL_GPL(vfio_pci_core_range_intersect_range);