/*
 * Copyright (c) 2014 Roger Pau Monné <roger.pau@citrix.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/kernel.h>
#include <sys/module.h>
#include <sys/pcpu.h>
#include <sys/rman.h>
#include <sys/smp.h>
#include <sys/limits.h>
#include <sys/vmmeter.h>

#include <vm/vm.h>
#include <vm/vm_page.h>
#include <vm/vm_param.h>
#include <vm/vm_phys.h>

#include <xen/xen-os.h>
#include <xen/gnttab.h>

#include "xenmem_if.h"

/*
 * Allocate unused physical memory above 4GB in order to map memory
 * from foreign domains. We use memory starting at 4GB in order to
 * prevent clashes with MMIO/ACPI regions.
 *
 * Since this is not possible on i386 just use any available memory
 * chunk above 1MB and hope we don't clash with anything else.
 *
 * Other architectures better document MMIO regions and drivers more
 * reliably reserve them.  As such, allow using any unpopulated memory
 * region.
 */
#ifdef __amd64__
#define LOW_MEM_LIMIT   0x100000000ul
#elif defined(__i386__)
#define LOW_MEM_LIMIT   0x100000ul
#else
#define LOW_MEM_LIMIT   0
#endif

/*
 * Memory ranges available for creating external mappings (foreign or grant
 * pages for example).
 */
static struct rman unpopulated_mem = {
        .rm_end = ~0,
        .rm_type = RMAN_ARRAY,
        .rm_descr = "Xen scratch memory",
};

static void
xenpv_identify(driver_t *driver, device_t parent)
{
        if (!xen_domain())
                return;

        /* Make sure there's only one xenpv device. */
        if (devclass_get_device(devclass_find(driver->name), 0))
                return;

        /*
         * The xenpv bus should be the last to attach in order
         * to properly detect if an ISA bus has already been added.
         */
        if (BUS_ADD_CHILD(parent, UINT_MAX, driver->name, 0) == NULL)
                panic("Unable to attach xenpv bus.");
}

static int
xenpv_probe(device_t dev)
{

        device_set_desc(dev, "Xen PV bus");
        return (BUS_PROBE_NOWILDCARD);
}

/* Dummy init for arches that don't have a specific implementation. */
int __weak_symbol
xen_arch_init_physmem(device_t dev, struct rman *mem)
{

        return (0);
}

static int
xenpv_attach(device_t dev)
{
        int error = rman_init(&unpopulated_mem);

        if (error != 0)
                return (error);

        error = xen_arch_init_physmem(dev, &unpopulated_mem);
        if (error != 0)
                return (error);

        /*
         * Let our child drivers identify any child devices that they
         * can find.  Once that is done attach any devices that we
         * found.
         */
        bus_identify_children(dev);
        bus_attach_children(dev);

        return (0);
}

static int
release_unpopulated_mem(device_t dev, struct resource *res)
{

        return (rman_is_region_manager(res, &unpopulated_mem) ?
            rman_release_resource(res) : bus_release_resource(dev, res));
}

static struct resource *
xenpv_alloc_physmem(device_t dev, device_t child, int *res_id, size_t size)
{
        struct resource *res;
        vm_paddr_t phys_addr;
        void *virt_addr;
        int error;
        const unsigned int flags = RF_ACTIVE | RF_UNMAPPED |
            RF_ALIGNMENT_LOG2(PAGE_SHIFT);

        KASSERT((size & PAGE_MASK) == 0, ("unaligned size requested"));
        size = round_page(size);

        /* Attempt to allocate from arch resource manager. */
        res = rman_reserve_resource(&unpopulated_mem, 0, ~0, size, flags,
            child);
        if (res != NULL) {
                rman_set_rid(res, *res_id);
                rman_set_type(res, SYS_RES_MEMORY);
        } else {
                static bool warned = false;

                /* Fallback to generic MMIO allocator. */
                if (__predict_false(!warned)) {
                        warned = true;
                        device_printf(dev,
                            "unable to allocate from arch specific routine, "
                            "fall back to unused memory areas\n");
                }
                res = bus_alloc_resource(child, SYS_RES_MEMORY, res_id,
                    LOW_MEM_LIMIT, ~0, size, flags);
        }

        if (res == NULL) {
                device_printf(dev,
                    "failed to allocate Xen unpopulated memory\n");
                return (NULL);
        }

        phys_addr = rman_get_start(res);
        error = vm_phys_fictitious_reg_range(phys_addr, phys_addr + size,
            VM_MEMATTR_XEN);
        if (error) {
                int error = release_unpopulated_mem(child, res);

                if (error != 0)
                        device_printf(dev, "failed to release resource: %d\n",
                            error);

                return (NULL);
        }
        virt_addr = pmap_mapdev_attr(phys_addr, size, VM_MEMATTR_XEN);
        KASSERT(virt_addr != NULL, ("Failed to create linear mappings"));
        rman_set_virtual(res, virt_addr);

        return (res);
}

static int
xenpv_free_physmem(device_t dev, device_t child, int res_id, struct resource *res)
{
        vm_paddr_t phys_addr;
        void *virt_addr;
        size_t size;

        phys_addr = rman_get_start(res);
        size = rman_get_size(res);
        virt_addr = rman_get_virtual(res);

        pmap_unmapdev(virt_addr, size);
        vm_phys_fictitious_unreg_range(phys_addr, phys_addr + size);

        return (release_unpopulated_mem(child, res));
}

static device_method_t xenpv_methods[] = {
        /* Device interface */
        DEVMETHOD(device_identify,              xenpv_identify),
        DEVMETHOD(device_probe,                 xenpv_probe),
        DEVMETHOD(device_attach,                xenpv_attach),
        DEVMETHOD(device_suspend,               bus_generic_suspend),
        DEVMETHOD(device_resume,                bus_generic_resume),

        /* Bus interface */
        DEVMETHOD(bus_add_child,                bus_generic_add_child),
        DEVMETHOD(bus_alloc_resource,           bus_generic_alloc_resource),
        DEVMETHOD(bus_release_resource,         bus_generic_release_resource),
        DEVMETHOD(bus_activate_resource,        bus_generic_activate_resource),
        DEVMETHOD(bus_deactivate_resource,      bus_generic_deactivate_resource),

        /* Interface to allocate memory for foreign mappings */
        DEVMETHOD(xenmem_alloc,                 xenpv_alloc_physmem),
        DEVMETHOD(xenmem_free,                  xenpv_free_physmem),

        DEVMETHOD_END
};

static driver_t xenpv_driver = {
        "xenpv",
        xenpv_methods,
        0,
};

DRIVER_MODULE(xenpv, nexus, xenpv_driver, 0, 0);

struct resource *
xenmem_alloc(device_t dev, int *res_id, size_t size)
{
        device_t parent;

        parent = device_get_parent(dev);
        if (parent == NULL)
                return (NULL);
        return (XENMEM_ALLOC(parent, dev, res_id, size));
}

int
xenmem_free(device_t dev, int res_id, struct resource *res)
{
        device_t parent;

        parent = device_get_parent(dev);
        if (parent == NULL)
                return (ENXIO);
        return (XENMEM_FREE(parent, dev, res_id, res));
}