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/*
* QEMU Xen emulation: Shared/overlay pages support
*
* Copyright © 2022 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Authors: David Woodhouse <dwmw2@infradead.org>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#include "qemu/osdep.h"
#include "qemu/host-utils.h"
#include "qemu/module.h"
#include "qemu/main-loop.h"
#include "qapi/error.h"
#include "qom/object.h"
#include "exec/target_page.h"
#include "exec/address-spaces.h"
#include "migration/vmstate.h"
#include "hw/sysbus.h"
#include "hw/xen/xen.h"
#include "xen_overlay.h"
#include "sysemu/kvm.h"
#include "sysemu/kvm_xen.h"
#include <linux/kvm.h>
#include "hw/xen/interface/memory.h"
#define TYPE_XEN_OVERLAY "xen-overlay"
OBJECT_DECLARE_SIMPLE_TYPE(XenOverlayState, XEN_OVERLAY)
#define XEN_PAGE_SHIFT 12
#define XEN_PAGE_SIZE (1ULL << XEN_PAGE_SHIFT)
struct XenOverlayState {
/*< private >*/
SysBusDevice busdev;
/*< public >*/
MemoryRegion shinfo_mem;
void *shinfo_ptr;
uint64_t shinfo_gpa;
};
struct XenOverlayState *xen_overlay_singleton;
static void xen_overlay_do_map_page(MemoryRegion *page, uint64_t gpa)
{
/*
* Xen allows guests to map the same page as many times as it likes
* into guest physical frames. We don't, because it would be hard
* to track and restore them all. One mapping of each page is
* perfectly sufficient for all known guests... and we've tested
* that theory on a few now in other implementations. dwmw2.
*/
if (memory_region_is_mapped(page)) {
if (gpa == INVALID_GPA) {
memory_region_del_subregion(get_system_memory(), page);
} else {
/* Just move it */
memory_region_set_address(page, gpa);
}
} else if (gpa != INVALID_GPA) {
memory_region_add_subregion_overlap(get_system_memory(), gpa, page, 0);
}
}
/* KVM is the only existing back end for now. Let's not overengineer it yet. */
static int xen_overlay_set_be_shinfo(uint64_t gfn)
{
struct kvm_xen_hvm_attr xa = {
.type = KVM_XEN_ATTR_TYPE_SHARED_INFO,
.u.shared_info.gfn = gfn,
};
return kvm_vm_ioctl(kvm_state, KVM_XEN_HVM_SET_ATTR, &xa);
}
static void xen_overlay_realize(DeviceState *dev, Error **errp)
{
XenOverlayState *s = XEN_OVERLAY(dev);
if (xen_mode != XEN_EMULATE) {
error_setg(errp, "Xen overlay page support is for Xen emulation");
return;
}
memory_region_init_ram(&s->shinfo_mem, OBJECT(dev), "xen:shared_info",
XEN_PAGE_SIZE, &error_abort);
memory_region_set_enabled(&s->shinfo_mem, true);
s->shinfo_ptr = memory_region_get_ram_ptr(&s->shinfo_mem);
s->shinfo_gpa = INVALID_GPA;
memset(s->shinfo_ptr, 0, XEN_PAGE_SIZE);
}
static int xen_overlay_post_load(void *opaque, int version_id)
{
XenOverlayState *s = opaque;
if (s->shinfo_gpa != INVALID_GPA) {
xen_overlay_do_map_page(&s->shinfo_mem, s->shinfo_gpa);
xen_overlay_set_be_shinfo(s->shinfo_gpa >> XEN_PAGE_SHIFT);
}
return 0;
}
static bool xen_overlay_is_needed(void *opaque)
{
return xen_mode == XEN_EMULATE;
}
static const VMStateDescription xen_overlay_vmstate = {
.name = "xen_overlay",
.version_id = 1,
.minimum_version_id = 1,
.needed = xen_overlay_is_needed,
.post_load = xen_overlay_post_load,
.fields = (VMStateField[]) {
VMSTATE_UINT64(shinfo_gpa, XenOverlayState),
VMSTATE_END_OF_LIST()
}
};
static void xen_overlay_reset(DeviceState *dev)
{
kvm_xen_soft_reset();
}
static void xen_overlay_class_init(ObjectClass *klass, void *data)
{
DeviceClass *dc = DEVICE_CLASS(klass);
dc->reset = xen_overlay_reset;
dc->realize = xen_overlay_realize;
dc->vmsd = &xen_overlay_vmstate;
}
static const TypeInfo xen_overlay_info = {
.name = TYPE_XEN_OVERLAY,
.parent = TYPE_SYS_BUS_DEVICE,
.instance_size = sizeof(XenOverlayState),
.class_init = xen_overlay_class_init,
};
void xen_overlay_create(void)
{
xen_overlay_singleton = XEN_OVERLAY(sysbus_create_simple(TYPE_XEN_OVERLAY,
-1, NULL));
/* If xen_domid wasn't explicitly set, at least make sure it isn't zero. */
if (xen_domid == DOMID_QEMU) {
xen_domid = 1;
};
}
static void xen_overlay_register_types(void)
{
type_register_static(&xen_overlay_info);
}
type_init(xen_overlay_register_types)
int xen_overlay_map_shinfo_page(uint64_t gpa)
{
XenOverlayState *s = xen_overlay_singleton;
int ret;
if (!s) {
return -ENOENT;
}
assert(qemu_mutex_iothread_locked());
if (s->shinfo_gpa) {
/* If removing shinfo page, turn the kernel magic off first */
ret = xen_overlay_set_be_shinfo(INVALID_GFN);
if (ret) {
return ret;
}
}
xen_overlay_do_map_page(&s->shinfo_mem, gpa);
if (gpa != INVALID_GPA) {
ret = xen_overlay_set_be_shinfo(gpa >> XEN_PAGE_SHIFT);
if (ret) {
return ret;
}
}
s->shinfo_gpa = gpa;
return 0;
}
void *xen_overlay_get_shinfo_ptr(void)
{
XenOverlayState *s = xen_overlay_singleton;
if (!s) {
return NULL;
}
return s->shinfo_ptr;
}
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