// SPDX-License-Identifier: GPL-2.0-only
/*
 * AMD Memory Encryption Support
 *
 * Copyright (C) 2019 SUSE
 *
 * Author: Joerg Roedel <jroedel@suse.de>
 */

#define pr_fmt(fmt)     "SEV: " fmt

#include <linux/sched/debug.h>  /* For show_regs() */
#include <linux/cc_platform.h>
#include <linux/printk.h>
#include <linux/mm_types.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/io.h>
#include <linux/psp-sev.h>
#include <linux/efi.h>
#include <uapi/linux/sev-guest.h>

#include <asm/init.h>
#include <asm/stacktrace.h>
#include <asm/sev.h>
#include <asm/insn-eval.h>
#include <asm/fpu/xcr.h>
#include <asm/processor.h>
#include <asm/setup.h>
#include <asm/traps.h>
#include <asm/svm.h>
#include <asm/smp.h>
#include <asm/cpu.h>
#include <asm/apic.h>
#include <asm/cpuid/api.h>

#include "internal.h"

static enum es_result vc_slow_virt_to_phys(struct ghcb *ghcb, struct es_em_ctxt *ctxt,
                                           unsigned long vaddr, phys_addr_t *paddr)
{
        unsigned long va = (unsigned long)vaddr;
        unsigned int level;
        phys_addr_t pa;
        pgd_t *pgd;
        pte_t *pte;

        pgd = __va(read_cr3_pa());
        pgd = &pgd[pgd_index(va)];
        pte = lookup_address_in_pgd(pgd, va, &level);
        if (!pte) {
                ctxt->fi.vector     = X86_TRAP_PF;
                ctxt->fi.cr2        = vaddr;
                ctxt->fi.error_code = 0;

                if (user_mode(ctxt->regs))
                        ctxt->fi.error_code |= X86_PF_USER;

                return ES_EXCEPTION;
        }

        if (WARN_ON_ONCE(pte_val(*pte) & _PAGE_ENC))
                /* Emulated MMIO to/from encrypted memory not supported */
                return ES_UNSUPPORTED;

        pa = (phys_addr_t)pte_pfn(*pte) << PAGE_SHIFT;
        pa |= va & ~page_level_mask(level);

        *paddr = pa;

        return ES_OK;
}

static enum es_result vc_ioio_check(struct es_em_ctxt *ctxt, u16 port, size_t size)
{
        BUG_ON(size > 4);

        if (user_mode(ctxt->regs)) {
                struct thread_struct *t = &current->thread;
                struct io_bitmap *iobm = t->io_bitmap;
                size_t idx;

                if (!iobm)
                        goto fault;

                for (idx = port; idx < port + size; ++idx) {
                        if (test_bit(idx, iobm->bitmap))
                                goto fault;
                }
        }

        return ES_OK;

fault:
        ctxt->fi.vector = X86_TRAP_GP;
        ctxt->fi.error_code = 0;

        return ES_EXCEPTION;
}

void vc_forward_exception(struct es_em_ctxt *ctxt)
{
        long error_code = ctxt->fi.error_code;
        int trapnr = ctxt->fi.vector;

        ctxt->regs->orig_ax = ctxt->fi.error_code;

        switch (trapnr) {
        case X86_TRAP_GP:
                exc_general_protection(ctxt->regs, error_code);
                break;
        case X86_TRAP_UD:
                exc_invalid_op(ctxt->regs);
                break;
        case X86_TRAP_PF:
                write_cr2(ctxt->fi.cr2);
                exc_page_fault(ctxt->regs, error_code);
                break;
        case X86_TRAP_AC:
                exc_alignment_check(ctxt->regs, error_code);
                break;
        default:
                pr_emerg("Unsupported exception in #VC instruction emulation - can't continue\n");
                BUG();
        }
}

static int vc_fetch_insn_kernel(struct es_em_ctxt *ctxt,
                                unsigned char *buffer)
{
        return copy_from_kernel_nofault(buffer, (unsigned char *)ctxt->regs->ip, MAX_INSN_SIZE);
}

static enum es_result __vc_decode_user_insn(struct es_em_ctxt *ctxt)
{
        char buffer[MAX_INSN_SIZE];
        int insn_bytes;

        insn_bytes = insn_fetch_from_user_inatomic(ctxt->regs, buffer);
        if (insn_bytes == 0) {
                /* Nothing could be copied */
                ctxt->fi.vector     = X86_TRAP_PF;
                ctxt->fi.error_code = X86_PF_INSTR | X86_PF_USER;
                ctxt->fi.cr2        = ctxt->regs->ip;
                return ES_EXCEPTION;
        } else if (insn_bytes == -EINVAL) {
                /* Effective RIP could not be calculated */
                ctxt->fi.vector     = X86_TRAP_GP;
                ctxt->fi.error_code = 0;
                ctxt->fi.cr2        = 0;
                return ES_EXCEPTION;
        }

        if (!insn_decode_from_regs(&ctxt->insn, ctxt->regs, buffer, insn_bytes))
                return ES_DECODE_FAILED;

        if (ctxt->insn.immediate.got)
                return ES_OK;
        else
                return ES_DECODE_FAILED;
}

static enum es_result __vc_decode_kern_insn(struct es_em_ctxt *ctxt)
{
        char buffer[MAX_INSN_SIZE];
        int res, ret;

        res = vc_fetch_insn_kernel(ctxt, buffer);
        if (res) {
                ctxt->fi.vector     = X86_TRAP_PF;
                ctxt->fi.error_code = X86_PF_INSTR;
                ctxt->fi.cr2        = ctxt->regs->ip;
                return ES_EXCEPTION;
        }

        ret = insn_decode(&ctxt->insn, buffer, MAX_INSN_SIZE, INSN_MODE_64);
        if (ret < 0)
                return ES_DECODE_FAILED;
        else
                return ES_OK;
}

/*
 * User instruction decoding is also required for the EFI runtime. Even though
 * the EFI runtime is running in kernel mode, it uses special EFI virtual
 * address mappings that require the use of efi_mm to properly address and
 * decode.
 */
static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt)
{
        if (user_mode(ctxt->regs) || mm_is_efi(current->active_mm))
                return __vc_decode_user_insn(ctxt);
        else
                return __vc_decode_kern_insn(ctxt);
}

static enum es_result vc_write_mem(struct es_em_ctxt *ctxt,
                                   char *dst, char *buf, size_t size)
{
        unsigned long error_code = X86_PF_PROT | X86_PF_WRITE;

        /*
         * This function uses __put_user() independent of whether kernel or user
         * memory is accessed. This works fine because __put_user() does no
         * sanity checks of the pointer being accessed. All that it does is
         * to report when the access failed.
         *
         * Also, this function runs in atomic context, so __put_user() is not
         * allowed to sleep. The page-fault handler detects that it is running
         * in atomic context and will not try to take mmap_sem and handle the
         * fault, so additional pagefault_enable()/disable() calls are not
         * needed.
         *
         * The access can't be done via copy_to_user() here because
         * vc_write_mem() must not use string instructions to access unsafe
         * memory. The reason is that MOVS is emulated by the #VC handler by
         * splitting the move up into a read and a write and taking a nested #VC
         * exception on whatever of them is the MMIO access. Using string
         * instructions here would cause infinite nesting.
         */
        switch (size) {
        case 1: {
                u8 d1;
                u8 __user *target = (u8 __user *)dst;

                memcpy(&d1, buf, 1);
                if (__put_user(d1, target))
                        goto fault;
                break;
        }
        case 2: {
                u16 d2;
                u16 __user *target = (u16 __user *)dst;

                memcpy(&d2, buf, 2);
                if (__put_user(d2, target))
                        goto fault;
                break;
        }
        case 4: {
                u32 d4;
                u32 __user *target = (u32 __user *)dst;

                memcpy(&d4, buf, 4);
                if (__put_user(d4, target))
                        goto fault;
                break;
        }
        case 8: {
                u64 d8;
                u64 __user *target = (u64 __user *)dst;

                memcpy(&d8, buf, 8);
                if (__put_user(d8, target))
                        goto fault;
                break;
        }
        default:
                WARN_ONCE(1, "%s: Invalid size: %zu\n", __func__, size);
                return ES_UNSUPPORTED;
        }

        return ES_OK;

fault:
        if (user_mode(ctxt->regs))
                error_code |= X86_PF_USER;

        ctxt->fi.vector = X86_TRAP_PF;
        ctxt->fi.error_code = error_code;
        ctxt->fi.cr2 = (unsigned long)dst;

        return ES_EXCEPTION;
}

static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
                                  char *src, char *buf, size_t size)
{
        unsigned long error_code = X86_PF_PROT;

        /*
         * This function uses __get_user() independent of whether kernel or user
         * memory is accessed. This works fine because __get_user() does no
         * sanity checks of the pointer being accessed. All that it does is
         * to report when the access failed.
         *
         * Also, this function runs in atomic context, so __get_user() is not
         * allowed to sleep. The page-fault handler detects that it is running
         * in atomic context and will not try to take mmap_sem and handle the
         * fault, so additional pagefault_enable()/disable() calls are not
         * needed.
         *
         * The access can't be done via copy_from_user() here because
         * vc_read_mem() must not use string instructions to access unsafe
         * memory. The reason is that MOVS is emulated by the #VC handler by
         * splitting the move up into a read and a write and taking a nested #VC
         * exception on whatever of them is the MMIO access. Using string
         * instructions here would cause infinite nesting.
         */
        switch (size) {
        case 1: {
                u8 d1;
                u8 __user *s = (u8 __user *)src;

                if (__get_user(d1, s))
                        goto fault;
                memcpy(buf, &d1, 1);
                break;
        }
        case 2: {
                u16 d2;
                u16 __user *s = (u16 __user *)src;

                if (__get_user(d2, s))
                        goto fault;
                memcpy(buf, &d2, 2);
                break;
        }
        case 4: {
                u32 d4;
                u32 __user *s = (u32 __user *)src;

                if (__get_user(d4, s))
                        goto fault;
                memcpy(buf, &d4, 4);
                break;
        }
        case 8: {
                u64 d8;
                u64 __user *s = (u64 __user *)src;
                if (__get_user(d8, s))
                        goto fault;
                memcpy(buf, &d8, 8);
                break;
        }
        default:
                WARN_ONCE(1, "%s: Invalid size: %zu\n", __func__, size);
                return ES_UNSUPPORTED;
        }

        return ES_OK;

fault:
        if (user_mode(ctxt->regs))
                error_code |= X86_PF_USER;

        ctxt->fi.vector = X86_TRAP_PF;
        ctxt->fi.error_code = error_code;
        ctxt->fi.cr2 = (unsigned long)src;

        return ES_EXCEPTION;
}

#define sev_printk(fmt, ...)            printk(fmt, ##__VA_ARGS__)
#define error(v)

#include "vc-shared.c"

/* Writes to the SVSM CAA MSR are ignored */
static enum es_result __vc_handle_msr_caa(struct pt_regs *regs, bool write)
{
        if (write)
                return ES_OK;

        regs->ax = lower_32_bits(this_cpu_read(svsm_caa_pa));
        regs->dx = upper_32_bits(this_cpu_read(svsm_caa_pa));

        return ES_OK;
}

/*
 * TSC related accesses should not exit to the hypervisor when a guest is
 * executing with Secure TSC enabled, so special handling is required for
 * accesses of MSR_IA32_TSC and MSR_AMD64_GUEST_TSC_FREQ.
 */
static enum es_result __vc_handle_secure_tsc_msrs(struct es_em_ctxt *ctxt, bool write)
{
        struct pt_regs *regs = ctxt->regs;
        u64 tsc;

        /*
         * Writing to MSR_IA32_TSC can cause subsequent reads of the TSC to
         * return undefined values, and GUEST_TSC_FREQ is read-only. Generate
         * a #GP on all writes.
         */
        if (write) {
                ctxt->fi.vector = X86_TRAP_GP;
                ctxt->fi.error_code = 0;
                return ES_EXCEPTION;
        }

        /*
         * GUEST_TSC_FREQ read should not be intercepted when Secure TSC is
         * enabled. Terminate the guest if a read is attempted.
         */
        if (regs->cx == MSR_AMD64_GUEST_TSC_FREQ)
                return ES_VMM_ERROR;

        /* Reads of MSR_IA32_TSC should return the current TSC value. */
        tsc = rdtsc_ordered();
        regs->ax = lower_32_bits(tsc);
        regs->dx = upper_32_bits(tsc);

        return ES_OK;
}

enum es_result __vc_handle_msr(struct ghcb *ghcb, struct es_em_ctxt *ctxt, bool write)
{
        struct pt_regs *regs = ctxt->regs;
        enum es_result ret;

        switch (regs->cx) {
        case MSR_SVSM_CAA:
                return __vc_handle_msr_caa(regs, write);
        case MSR_IA32_TSC:
        case MSR_AMD64_GUEST_TSC_FREQ:
                if (sev_status & MSR_AMD64_SNP_SECURE_TSC)
                        return __vc_handle_secure_tsc_msrs(ctxt, write);
                break;
        case MSR_AMD64_SAVIC_CONTROL:
                /*
                 * AMD64_SAVIC_CONTROL should not be intercepted when
                 * Secure AVIC is enabled. Terminate the Secure AVIC guest
                 * if the interception is enabled.
                 */
                if (cc_platform_has(CC_ATTR_SNP_SECURE_AVIC))
                        return ES_VMM_ERROR;
                break;
        default:
                break;
        }

        ghcb_set_rcx(ghcb, regs->cx);
        if (write) {
                ghcb_set_rax(ghcb, regs->ax);
                ghcb_set_rdx(ghcb, regs->dx);
        }

        ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_MSR, write, 0);

        if ((ret == ES_OK) && !write) {
                regs->ax = ghcb->save.rax;
                regs->dx = ghcb->save.rdx;
        }

        return ret;
}

static enum es_result vc_handle_msr(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
{
        return __vc_handle_msr(ghcb, ctxt, ctxt->insn.opcode.bytes[1] == 0x30);
}

static void __init vc_early_forward_exception(struct es_em_ctxt *ctxt)
{
        int trapnr = ctxt->fi.vector;

        if (trapnr == X86_TRAP_PF)
                native_write_cr2(ctxt->fi.cr2);

        ctxt->regs->orig_ax = ctxt->fi.error_code;
        do_early_exception(ctxt->regs, trapnr);
}

static long *vc_insn_get_rm(struct es_em_ctxt *ctxt)
{
        long *reg_array;
        int offset;

        reg_array = (long *)ctxt->regs;
        offset    = insn_get_modrm_rm_off(&ctxt->insn, ctxt->regs);

        if (offset < 0)
                return NULL;

        offset /= sizeof(long);

        return reg_array + offset;
}
static enum es_result vc_do_mmio(struct ghcb *ghcb, struct es_em_ctxt *ctxt,
                                 unsigned int bytes, bool read)
{
        u64 exit_code, exit_info_1, exit_info_2;
        unsigned long ghcb_pa = __pa(ghcb);
        enum es_result res;
        phys_addr_t paddr;
        void __user *ref;

        ref = insn_get_addr_ref(&ctxt->insn, ctxt->regs);
        if (ref == (void __user *)-1L)
                return ES_UNSUPPORTED;

        exit_code = read ? SVM_VMGEXIT_MMIO_READ : SVM_VMGEXIT_MMIO_WRITE;

        res = vc_slow_virt_to_phys(ghcb, ctxt, (unsigned long)ref, &paddr);
        if (res != ES_OK) {
                if (res == ES_EXCEPTION && !read)
                        ctxt->fi.error_code |= X86_PF_WRITE;

                return res;
        }

        exit_info_1 = paddr;
        /* Can never be greater than 8 */
        exit_info_2 = bytes;

        ghcb_set_sw_scratch(ghcb, ghcb_pa + offsetof(struct ghcb, shared_buffer));

        return sev_es_ghcb_hv_call(ghcb, ctxt, exit_code, exit_info_1, exit_info_2);
}

/*
 * The MOVS instruction has two memory operands, which raises the
 * problem that it is not known whether the access to the source or the
 * destination caused the #VC exception (and hence whether an MMIO read
 * or write operation needs to be emulated).
 *
 * Instead of playing games with walking page-tables and trying to guess
 * whether the source or destination is an MMIO range, split the move
 * into two operations, a read and a write with only one memory operand.
 * This will cause a nested #VC exception on the MMIO address which can
 * then be handled.
 *
 * This implementation has the benefit that it also supports MOVS where
 * source _and_ destination are MMIO regions.
 *
 * It will slow MOVS on MMIO down a lot, but in SEV-ES guests it is a
 * rare operation. If it turns out to be a performance problem the split
 * operations can be moved to memcpy_fromio() and memcpy_toio().
 */
static enum es_result vc_handle_mmio_movs(struct es_em_ctxt *ctxt,
                                          unsigned int bytes)
{
        unsigned long ds_base, es_base;
        unsigned char *src, *dst;
        unsigned char buffer[8];
        enum es_result ret;
        bool rep;
        int off;

        ds_base = insn_get_seg_base(ctxt->regs, INAT_SEG_REG_DS);
        es_base = insn_get_seg_base(ctxt->regs, INAT_SEG_REG_ES);

        if (ds_base == -1L || es_base == -1L) {
                ctxt->fi.vector = X86_TRAP_GP;
                ctxt->fi.error_code = 0;
                return ES_EXCEPTION;
        }

        src = ds_base + (unsigned char *)ctxt->regs->si;
        dst = es_base + (unsigned char *)ctxt->regs->di;

        ret = vc_read_mem(ctxt, src, buffer, bytes);
        if (ret != ES_OK)
                return ret;

        ret = vc_write_mem(ctxt, dst, buffer, bytes);
        if (ret != ES_OK)
                return ret;

        if (ctxt->regs->flags & X86_EFLAGS_DF)
                off = -bytes;
        else
                off =  bytes;

        ctxt->regs->si += off;
        ctxt->regs->di += off;

        rep = insn_has_rep_prefix(&ctxt->insn);
        if (rep)
                ctxt->regs->cx -= 1;

        if (!rep || ctxt->regs->cx == 0)
                return ES_OK;
        else
                return ES_RETRY;
}

static enum es_result vc_handle_mmio(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
{
        struct insn *insn = &ctxt->insn;
        enum insn_mmio_type mmio;
        unsigned int bytes = 0;
        enum es_result ret;
        u8 sign_byte;
        long *reg_data;

        mmio = insn_decode_mmio(insn, &bytes);
        if (mmio == INSN_MMIO_DECODE_FAILED)
                return ES_DECODE_FAILED;

        if (mmio != INSN_MMIO_WRITE_IMM && mmio != INSN_MMIO_MOVS) {
                reg_data = insn_get_modrm_reg_ptr(insn, ctxt->regs);
                if (!reg_data)
                        return ES_DECODE_FAILED;
        }

        if (user_mode(ctxt->regs))
                return ES_UNSUPPORTED;

        switch (mmio) {
        case INSN_MMIO_WRITE:
                memcpy(ghcb->shared_buffer, reg_data, bytes);
                ret = vc_do_mmio(ghcb, ctxt, bytes, false);
                break;
        case INSN_MMIO_WRITE_IMM:
                memcpy(ghcb->shared_buffer, insn->immediate1.bytes, bytes);
                ret = vc_do_mmio(ghcb, ctxt, bytes, false);
                break;
        case INSN_MMIO_READ:
                ret = vc_do_mmio(ghcb, ctxt, bytes, true);
                if (ret)
                        break;

                /* Zero-extend for 32-bit operation */
                if (bytes == 4)
                        *reg_data = 0;

                memcpy(reg_data, ghcb->shared_buffer, bytes);
                break;
        case INSN_MMIO_READ_ZERO_EXTEND:
                ret = vc_do_mmio(ghcb, ctxt, bytes, true);
                if (ret)
                        break;

                /* Zero extend based on operand size */
                memset(reg_data, 0, insn->opnd_bytes);
                memcpy(reg_data, ghcb->shared_buffer, bytes);
                break;
        case INSN_MMIO_READ_SIGN_EXTEND:
                ret = vc_do_mmio(ghcb, ctxt, bytes, true);
                if (ret)
                        break;

                if (bytes == 1) {
                        u8 *val = (u8 *)ghcb->shared_buffer;

                        sign_byte = (*val & 0x80) ? 0xff : 0x00;
                } else {
                        u16 *val = (u16 *)ghcb->shared_buffer;

                        sign_byte = (*val & 0x8000) ? 0xff : 0x00;
                }

                /* Sign extend based on operand size */
                memset(reg_data, sign_byte, insn->opnd_bytes);
                memcpy(reg_data, ghcb->shared_buffer, bytes);
                break;
        case INSN_MMIO_MOVS:
                ret = vc_handle_mmio_movs(ctxt, bytes);
                break;
        default:
                ret = ES_UNSUPPORTED;
                break;
        }

        return ret;
}

static enum es_result vc_handle_dr7_write(struct ghcb *ghcb,
                                          struct es_em_ctxt *ctxt)
{
        struct sev_es_runtime_data *data = this_cpu_read(runtime_data);
        long val, *reg = vc_insn_get_rm(ctxt);
        enum es_result ret;

        if (sev_status & MSR_AMD64_SNP_DEBUG_SWAP)
                return ES_VMM_ERROR;

        if (!reg)
                return ES_DECODE_FAILED;

        val = *reg;

        /* Upper 32 bits must be written as zeroes */
        if (val >> 32) {
                ctxt->fi.vector = X86_TRAP_GP;
                ctxt->fi.error_code = 0;
                return ES_EXCEPTION;
        }

        /* Clear out other reserved bits and set bit 10 */
        val = (val & 0xffff23ffL) | BIT(10);

        /* Early non-zero writes to DR7 are not supported */
        if (!data && (val & ~DR7_RESET_VALUE))
                return ES_UNSUPPORTED;

        /* Using a value of 0 for ExitInfo1 means RAX holds the value */
        ghcb_set_rax(ghcb, val);
        ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_WRITE_DR7, 0, 0);
        if (ret != ES_OK)
                return ret;

        if (data)
                data->dr7 = val;

        return ES_OK;
}

static enum es_result vc_handle_dr7_read(struct ghcb *ghcb,
                                         struct es_em_ctxt *ctxt)
{
        struct sev_es_runtime_data *data = this_cpu_read(runtime_data);
        long *reg = vc_insn_get_rm(ctxt);

        if (sev_status & MSR_AMD64_SNP_DEBUG_SWAP)
                return ES_VMM_ERROR;

        if (!reg)
                return ES_DECODE_FAILED;

        if (data)
                *reg = data->dr7;
        else
                *reg = DR7_RESET_VALUE;

        return ES_OK;
}

static enum es_result vc_handle_wbinvd(struct ghcb *ghcb,
                                       struct es_em_ctxt *ctxt)
{
        return sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_WBINVD, 0, 0);
}

static enum es_result vc_handle_rdpmc(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
{
        enum es_result ret;

        ghcb_set_rcx(ghcb, ctxt->regs->cx);

        ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_RDPMC, 0, 0);
        if (ret != ES_OK)
                return ret;

        if (!(ghcb_rax_is_valid(ghcb) && ghcb_rdx_is_valid(ghcb)))
                return ES_VMM_ERROR;

        ctxt->regs->ax = ghcb->save.rax;
        ctxt->regs->dx = ghcb->save.rdx;

        return ES_OK;
}

static enum es_result vc_handle_monitor(struct ghcb *ghcb,
                                        struct es_em_ctxt *ctxt)
{
        /*
         * Treat it as a NOP and do not leak a physical address to the
         * hypervisor.
         */
        return ES_OK;
}

static enum es_result vc_handle_mwait(struct ghcb *ghcb,
                                      struct es_em_ctxt *ctxt)
{
        /* Treat the same as MONITOR/MONITORX */
        return ES_OK;
}

static enum es_result vc_handle_vmmcall(struct ghcb *ghcb,
                                        struct es_em_ctxt *ctxt)
{
        enum es_result ret;

        ghcb_set_rax(ghcb, ctxt->regs->ax);
        ghcb_set_cpl(ghcb, user_mode(ctxt->regs) ? 3 : 0);

        if (x86_platform.hyper.sev_es_hcall_prepare)
                x86_platform.hyper.sev_es_hcall_prepare(ghcb, ctxt->regs);

        ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_VMMCALL, 0, 0);
        if (ret != ES_OK)
                return ret;

        if (!ghcb_rax_is_valid(ghcb))
                return ES_VMM_ERROR;

        ctxt->regs->ax = ghcb->save.rax;

        /*
         * Call sev_es_hcall_finish() after regs->ax is already set.
         * This allows the hypervisor handler to overwrite it again if
         * necessary.
         */
        if (x86_platform.hyper.sev_es_hcall_finish &&
            !x86_platform.hyper.sev_es_hcall_finish(ghcb, ctxt->regs))
                return ES_VMM_ERROR;

        return ES_OK;
}

static enum es_result vc_handle_trap_ac(struct ghcb *ghcb,
                                        struct es_em_ctxt *ctxt)
{
        /*
         * Calling ecx_alignment_check() directly does not work, because it
         * enables IRQs and the GHCB is active. Forward the exception and call
         * it later from vc_forward_exception().
         */
        ctxt->fi.vector = X86_TRAP_AC;
        ctxt->fi.error_code = 0;
        return ES_EXCEPTION;
}

static enum es_result vc_handle_exitcode(struct es_em_ctxt *ctxt,
                                         struct ghcb *ghcb,
                                         unsigned long exit_code)
{
        enum es_result result = vc_check_opcode_bytes(ctxt, exit_code);

        if (result != ES_OK)
                return result;

        switch (exit_code) {
        case SVM_EXIT_READ_DR7:
                result = vc_handle_dr7_read(ghcb, ctxt);
                break;
        case SVM_EXIT_WRITE_DR7:
                result = vc_handle_dr7_write(ghcb, ctxt);
                break;
        case SVM_EXIT_EXCP_BASE + X86_TRAP_AC:
                result = vc_handle_trap_ac(ghcb, ctxt);
                break;
        case SVM_EXIT_RDTSC:
        case SVM_EXIT_RDTSCP:
                result = vc_handle_rdtsc(ghcb, ctxt, exit_code);
                break;
        case SVM_EXIT_RDPMC:
                result = vc_handle_rdpmc(ghcb, ctxt);
                break;
        case SVM_EXIT_INVD:
                pr_err_ratelimited("#VC exception for INVD??? Seriously???\n");
                result = ES_UNSUPPORTED;
                break;
        case SVM_EXIT_CPUID:
                result = vc_handle_cpuid(ghcb, ctxt);
                break;
        case SVM_EXIT_IOIO:
                result = vc_handle_ioio(ghcb, ctxt);
                break;
        case SVM_EXIT_MSR:
                result = vc_handle_msr(ghcb, ctxt);
                break;
        case SVM_EXIT_VMMCALL:
                result = vc_handle_vmmcall(ghcb, ctxt);
                break;
        case SVM_EXIT_WBINVD:
                result = vc_handle_wbinvd(ghcb, ctxt);
                break;
        case SVM_EXIT_MONITOR:
                result = vc_handle_monitor(ghcb, ctxt);
                break;
        case SVM_EXIT_MWAIT:
                result = vc_handle_mwait(ghcb, ctxt);
                break;
        case SVM_EXIT_NPF:
                result = vc_handle_mmio(ghcb, ctxt);
                break;
        default:
                /*
                 * Unexpected #VC exception
                 */
                result = ES_UNSUPPORTED;
        }

        return result;
}

static __always_inline bool is_vc2_stack(unsigned long sp)
{
        return (sp >= __this_cpu_ist_bottom_va(VC2) && sp < __this_cpu_ist_top_va(VC2));
}

static __always_inline bool vc_from_invalid_context(struct pt_regs *regs)
{
        unsigned long sp, prev_sp;

        sp      = (unsigned long)regs;
        prev_sp = regs->sp;

        /*
         * If the code was already executing on the VC2 stack when the #VC
         * happened, let it proceed to the normal handling routine. This way the
         * code executing on the VC2 stack can cause #VC exceptions to get handled.
         */
        return is_vc2_stack(sp) && !is_vc2_stack(prev_sp);
}

static bool vc_raw_handle_exception(struct pt_regs *regs, unsigned long error_code)
{
        struct ghcb_state state;
        struct es_em_ctxt ctxt;
        enum es_result result;
        struct ghcb *ghcb;
        bool ret = true;

        ghcb = __sev_get_ghcb(&state);

        vc_ghcb_invalidate(ghcb);
        result = vc_init_em_ctxt(&ctxt, regs, error_code);

        if (result == ES_OK)
                result = vc_handle_exitcode(&ctxt, ghcb, error_code);

        __sev_put_ghcb(&state);

        /* Done - now check the result */
        switch (result) {
        case ES_OK:
                vc_finish_insn(&ctxt);
                break;
        case ES_UNSUPPORTED:
                pr_err_ratelimited("Unsupported exit-code 0x%02lx in #VC exception (IP: 0x%lx)\n",
                                   error_code, regs->ip);
                ret = false;
                break;
        case ES_VMM_ERROR:
                pr_err_ratelimited("Failure in communication with VMM (exit-code 0x%02lx IP: 0x%lx)\n",
                                   error_code, regs->ip);
                ret = false;
                break;
        case ES_DECODE_FAILED:
                pr_err_ratelimited("Failed to decode instruction (exit-code 0x%02lx IP: 0x%lx)\n",
                                   error_code, regs->ip);
                ret = false;
                break;
        case ES_EXCEPTION:
                vc_forward_exception(&ctxt);
                break;
        case ES_RETRY:
                /* Nothing to do */
                break;
        default:
                pr_emerg("Unknown result in %s():%d\n", __func__, result);
                /*
                 * Emulating the instruction which caused the #VC exception
                 * failed - can't continue so print debug information
                 */
                BUG();
        }

        return ret;
}

static __always_inline bool vc_is_db(unsigned long error_code)
{
        return error_code == SVM_EXIT_EXCP_BASE + X86_TRAP_DB;
}

/*
 * Runtime #VC exception handler when raised from kernel mode. Runs in NMI mode
 * and will panic when an error happens.
 */
DEFINE_IDTENTRY_VC_KERNEL(exc_vmm_communication)
{
        irqentry_state_t irq_state;

        /*
         * With the current implementation it is always possible to switch to a
         * safe stack because #VC exceptions only happen at known places, like
         * intercepted instructions or accesses to MMIO areas/IO ports. They can
         * also happen with code instrumentation when the hypervisor intercepts
         * #DB, but the critical paths are forbidden to be instrumented, so #DB
         * exceptions currently also only happen in safe places.
         *
         * But keep this here in case the noinstr annotations are violated due
         * to bug elsewhere.
         */
        if (unlikely(vc_from_invalid_context(regs))) {
                instrumentation_begin();
                panic("Can't handle #VC exception from unsupported context\n");
                instrumentation_end();
        }

        /*
         * Handle #DB before calling into !noinstr code to avoid recursive #DB.
         */
        if (vc_is_db(error_code)) {
                exc_debug(regs);
                return;
        }

        irq_state = irqentry_nmi_enter(regs);

        instrumentation_begin();

        if (!vc_raw_handle_exception(regs, error_code)) {
                /* Show some debug info */
                show_regs(regs);

                /* Ask hypervisor to sev_es_terminate */
                sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ);

                /* If that fails and we get here - just panic */
                panic("Returned from Terminate-Request to Hypervisor\n");
        }

        instrumentation_end();
        irqentry_nmi_exit(regs, irq_state);
}

/*
 * Runtime #VC exception handler when raised from user mode. Runs in IRQ mode
 * and will kill the current task with SIGBUS when an error happens.
 */
DEFINE_IDTENTRY_VC_USER(exc_vmm_communication)
{
        /*
         * Handle #DB before calling into !noinstr code to avoid recursive #DB.
         */
        if (vc_is_db(error_code)) {
                noist_exc_debug(regs);
                return;
        }

        irqentry_enter_from_user_mode(regs);
        instrumentation_begin();

        if (!vc_raw_handle_exception(regs, error_code)) {
                /*
                 * Do not kill the machine if user-space triggered the
                 * exception. Send SIGBUS instead and let user-space deal with
                 * it.
                 */
                force_sig_fault(SIGBUS, BUS_OBJERR, (void __user *)0);
        }

        instrumentation_end();
        irqentry_exit_to_user_mode(regs);
}

bool __init handle_vc_boot_ghcb(struct pt_regs *regs)
{
        unsigned long exit_code = regs->orig_ax;
        struct es_em_ctxt ctxt;
        enum es_result result;

        vc_ghcb_invalidate(boot_ghcb);

        result = vc_init_em_ctxt(&ctxt, regs, exit_code);
        if (result == ES_OK)
                result = vc_handle_exitcode(&ctxt, boot_ghcb, exit_code);

        /* Done - now check the result */
        switch (result) {
        case ES_OK:
                vc_finish_insn(&ctxt);
                break;
        case ES_UNSUPPORTED:
                early_printk("PANIC: Unsupported exit-code 0x%02lx in early #VC exception (IP: 0x%lx)\n",
                                exit_code, regs->ip);
                goto fail;
        case ES_VMM_ERROR:
                early_printk("PANIC: Failure in communication with VMM (exit-code 0x%02lx IP: 0x%lx)\n",
                                exit_code, regs->ip);
                goto fail;
        case ES_DECODE_FAILED:
                early_printk("PANIC: Failed to decode instruction (exit-code 0x%02lx IP: 0x%lx)\n",
                                exit_code, regs->ip);
                goto fail;
        case ES_EXCEPTION:
                vc_early_forward_exception(&ctxt);
                break;
        case ES_RETRY:
                /* Nothing to do */
                break;
        default:
                BUG();
        }

        return true;

fail:
        show_regs(regs);

        sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ);
}