Google Git
Sign in
qemu / qemu / 9cdafe3b47ce2d5e4f609391fb680403ed3f0716 / . / hw / i386 / kvm / xen_gnttab.c
blob: 0a24f53f20ed752b75be483f09a7a199ab4dcc73 [file] [log] [blame]
/*
* QEMU Xen emulation: Grant table 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/lockable.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 "hw/xen/xen_backend_ops.h"
#include "xen_overlay.h"
#include "xen_gnttab.h"
#include "xen_primary_console.h"
#include "sysemu/kvm.h"
#include "sysemu/kvm_xen.h"
#include "hw/xen/interface/memory.h"
#include "hw/xen/interface/grant_table.h"
#define TYPE_XEN_GNTTAB "xen-gnttab"
OBJECT_DECLARE_SIMPLE_TYPE(XenGnttabState, XEN_GNTTAB)
#define ENTRIES_PER_FRAME_V1 (XEN_PAGE_SIZE / sizeof(grant_entry_v1_t))
static struct gnttab_backend_ops emu_gnttab_backend_ops;
struct XenGnttabState {
/*< private >*/
SysBusDevice busdev;
/*< public >*/
QemuMutex gnt_lock;
uint32_t nr_frames;
uint32_t max_frames;
union {
grant_entry_v1_t *v1;
/* Theoretically, v2 support could be added here. */
} entries;
MemoryRegion gnt_frames;
MemoryRegion *gnt_aliases;
uint64_t *gnt_frame_gpas;
uint8_t *map_track;
};
struct XenGnttabState *xen_gnttab_singleton;
static void xen_gnttab_realize(DeviceState *dev, Error **errp)
{
XenGnttabState *s = XEN_GNTTAB(dev);
int i;
if (xen_mode != XEN_EMULATE) {
error_setg(errp, "Xen grant table support is for Xen emulation");
return;
}
s->max_frames = kvm_xen_get_gnttab_max_frames();
memory_region_init_ram(&s->gnt_frames, OBJECT(dev), "xen:grant_table",
XEN_PAGE_SIZE * s->max_frames, &error_abort);
memory_region_set_enabled(&s->gnt_frames, true);
s->entries.v1 = memory_region_get_ram_ptr(&s->gnt_frames);
/* Create individual page-sizes aliases for overlays */
s->gnt_aliases = (void *)g_new0(MemoryRegion, s->max_frames);
s->gnt_frame_gpas = (void *)g_new(uint64_t, s->max_frames);
for (i = 0; i < s->max_frames; i++) {
memory_region_init_alias(&s->gnt_aliases[i], OBJECT(dev),
NULL, &s->gnt_frames,
i * XEN_PAGE_SIZE, XEN_PAGE_SIZE);
s->gnt_frame_gpas[i] = INVALID_GPA;
}
s->nr_frames = 0;
memset(s->entries.v1, 0, XEN_PAGE_SIZE * s->max_frames);
s->entries.v1[GNTTAB_RESERVED_XENSTORE].flags = GTF_permit_access;
s->entries.v1[GNTTAB_RESERVED_XENSTORE].frame = XEN_SPECIAL_PFN(XENSTORE);
qemu_mutex_init(&s->gnt_lock);
xen_gnttab_singleton = s;
s->map_track = g_new0(uint8_t, s->max_frames * ENTRIES_PER_FRAME_V1);
xen_gnttab_ops = &emu_gnttab_backend_ops;
}
static int xen_gnttab_post_load(void *opaque, int version_id)
{
XenGnttabState *s = XEN_GNTTAB(opaque);
uint32_t i;
for (i = 0; i < s->nr_frames; i++) {
if (s->gnt_frame_gpas[i] != INVALID_GPA) {
xen_overlay_do_map_page(&s->gnt_aliases[i], s->gnt_frame_gpas[i]);
}
}
return 0;
}
static bool xen_gnttab_is_needed(void *opaque)
{
return xen_mode == XEN_EMULATE;
}
static const VMStateDescription xen_gnttab_vmstate = {
.name = "xen_gnttab",
.version_id = 1,
.minimum_version_id = 1,
.needed = xen_gnttab_is_needed,
.post_load = xen_gnttab_post_load,
.fields = (VMStateField[]) {
VMSTATE_UINT32(nr_frames, XenGnttabState),
VMSTATE_VARRAY_UINT32(gnt_frame_gpas, XenGnttabState, nr_frames, 0,
vmstate_info_uint64, uint64_t),
VMSTATE_END_OF_LIST()
}
};
static void xen_gnttab_class_init(ObjectClass *klass, void *data)
{
DeviceClass *dc = DEVICE_CLASS(klass);
dc->realize = xen_gnttab_realize;
dc->vmsd = &xen_gnttab_vmstate;
}
static const TypeInfo xen_gnttab_info = {
.name = TYPE_XEN_GNTTAB,
.parent = TYPE_SYS_BUS_DEVICE,
.instance_size = sizeof(XenGnttabState),
.class_init = xen_gnttab_class_init,
};
void xen_gnttab_create(void)
{
xen_gnttab_singleton = XEN_GNTTAB(sysbus_create_simple(TYPE_XEN_GNTTAB,
-1, NULL));
}
static void xen_gnttab_register_types(void)
{
type_register_static(&xen_gnttab_info);
}
type_init(xen_gnttab_register_types)
int xen_gnttab_map_page(uint64_t idx, uint64_t gfn)
{
XenGnttabState *s = xen_gnttab_singleton;
uint64_t gpa = gfn << XEN_PAGE_SHIFT;
if (!s) {
return -ENOTSUP;
}
if (idx >= s->max_frames) {
return -EINVAL;
}
QEMU_IOTHREAD_LOCK_GUARD();
QEMU_LOCK_GUARD(&s->gnt_lock);
xen_overlay_do_map_page(&s->gnt_aliases[idx], gpa);
s->gnt_frame_gpas[idx] = gpa;
if (s->nr_frames <= idx) {
s->nr_frames = idx + 1;
}
return 0;
}
int xen_gnttab_set_version_op(struct gnttab_set_version *set)
{
int ret;
switch (set->version) {
case 1:
ret = 0;
break;
case 2:
/* Behave as before set_version was introduced. */
ret = -ENOSYS;
break;
default:
ret = -EINVAL;
}
set->version = 1;
return ret;
}
int xen_gnttab_get_version_op(struct gnttab_get_version *get)
{
if (get->dom != DOMID_SELF && get->dom != xen_domid) {
return -ESRCH;
}
get->version = 1;
return 0;
}
int xen_gnttab_query_size_op(struct gnttab_query_size *size)
{
XenGnttabState *s = xen_gnttab_singleton;
if (!s) {
return -ENOTSUP;
}
if (size->dom != DOMID_SELF && size->dom != xen_domid) {
size->status = GNTST_bad_domain;
return 0;
}
size->status = GNTST_okay;
size->nr_frames = s->nr_frames;
size->max_nr_frames = s->max_frames;
return 0;
}
/* Track per-open refs, to allow close() to clean up. */
struct active_ref {
MemoryRegionSection mrs;
void *virtaddr;
uint32_t refcnt;
int prot;
};
static void gnt_unref(XenGnttabState *s, grant_ref_t ref,
MemoryRegionSection *mrs, int prot)
{
if (mrs && mrs->mr) {
if (prot & PROT_WRITE) {
memory_region_set_dirty(mrs->mr, mrs->offset_within_region,
XEN_PAGE_SIZE);
}
memory_region_unref(mrs->mr);
mrs->mr = NULL;
}
assert(s->map_track[ref] != 0);
if (--s->map_track[ref] == 0) {
grant_entry_v1_t *gnt_p = &s->entries.v1[ref];
qatomic_and(&gnt_p->flags, (uint16_t)~(GTF_reading | GTF_writing));
}
}
static uint64_t gnt_ref(XenGnttabState *s, grant_ref_t ref, int prot)
{
uint16_t mask = GTF_type_mask | GTF_sub_page;
grant_entry_v1_t gnt, *gnt_p;
int retries = 0;
if (ref >= s->max_frames * ENTRIES_PER_FRAME_V1 ||
s->map_track[ref] == UINT8_MAX) {
return INVALID_GPA;
}
if (prot & PROT_WRITE) {
mask |= GTF_readonly;
}
gnt_p = &s->entries.v1[ref];
/*
* The guest can legitimately be changing the GTF_readonly flag. Allow
* that, but don't let a malicious guest cause a livelock.
*/
for (retries = 0; retries < 5; retries++) {
uint16_t new_flags;
/* Read the entry before an atomic operation on its flags */
gnt = *(volatile grant_entry_v1_t *)gnt_p;
if ((gnt.flags & mask) != GTF_permit_access ||
gnt.domid != DOMID_QEMU) {
return INVALID_GPA;
}
new_flags = gnt.flags | GTF_reading;
if (prot & PROT_WRITE) {
new_flags |= GTF_writing;
}
if (qatomic_cmpxchg(&gnt_p->flags, gnt.flags, new_flags) == gnt.flags) {
return (uint64_t)gnt.frame << XEN_PAGE_SHIFT;
}
}
return INVALID_GPA;
}
struct xengntdev_handle {
GHashTable *active_maps;
};
static int xen_be_gnttab_set_max_grants(struct xengntdev_handle *xgt,
uint32_t nr_grants)
{
return 0;
}
static void *xen_be_gnttab_map_refs(struct xengntdev_handle *xgt,
uint32_t count, uint32_t domid,
uint32_t *refs, int prot)
{
XenGnttabState *s = xen_gnttab_singleton;
struct active_ref *act;
if (!s) {
errno = ENOTSUP;
return NULL;
}
if (domid != xen_domid) {
errno = EINVAL;
return NULL;
}
if (!count || count > 4096) {
errno = EINVAL;
return NULL;
}
/*
* Making a contiguous mapping from potentially discontiguous grant
* references would be... distinctly non-trivial. We don't support it.
* Even changing the API to return an array of pointers, one per page,
* wouldn't be simple to use in PV backends because some structures
* actually cross page boundaries (e.g. 32-bit blkif_response ring
* entries are 12 bytes).
*/
if (count != 1) {
errno = EINVAL;
return NULL;
}
QEMU_LOCK_GUARD(&s->gnt_lock);
act = g_hash_table_lookup(xgt->active_maps, GINT_TO_POINTER(refs[0]));
if (act) {
if ((prot & PROT_WRITE) && !(act->prot & PROT_WRITE)) {
if (gnt_ref(s, refs[0], prot) == INVALID_GPA) {
return NULL;
}
act->prot |= PROT_WRITE;
}
act->refcnt++;
} else {
uint64_t gpa = gnt_ref(s, refs[0], prot);
if (gpa == INVALID_GPA) {
errno = EINVAL;
return NULL;
}
act = g_new0(struct active_ref, 1);
act->prot = prot;
act->refcnt = 1;
act->mrs = memory_region_find(get_system_memory(), gpa, XEN_PAGE_SIZE);
if (act->mrs.mr &&
!int128_lt(act->mrs.size, int128_make64(XEN_PAGE_SIZE)) &&
memory_region_get_ram_addr(act->mrs.mr) != RAM_ADDR_INVALID) {
act->virtaddr = qemu_map_ram_ptr(act->mrs.mr->ram_block,
act->mrs.offset_within_region);
}
if (!act->virtaddr) {
gnt_unref(s, refs[0], &act->mrs, 0);
g_free(act);
errno = EINVAL;
return NULL;
}
s->map_track[refs[0]]++;
g_hash_table_insert(xgt->active_maps, GINT_TO_POINTER(refs[0]), act);
}
return act->virtaddr;
}
static gboolean do_unmap(gpointer key, gpointer value, gpointer user_data)
{
XenGnttabState *s = user_data;
grant_ref_t gref = GPOINTER_TO_INT(key);
struct active_ref *act = value;
gnt_unref(s, gref, &act->mrs, act->prot);
g_free(act);
return true;
}
static int xen_be_gnttab_unmap(struct xengntdev_handle *xgt,
void *start_address, uint32_t *refs,
uint32_t count)
{
XenGnttabState *s = xen_gnttab_singleton;
struct active_ref *act;
if (!s) {
return -ENOTSUP;
}
if (count != 1) {
return -EINVAL;
}
QEMU_LOCK_GUARD(&s->gnt_lock);
act = g_hash_table_lookup(xgt->active_maps, GINT_TO_POINTER(refs[0]));
if (!act) {
return -ENOENT;
}
if (act->virtaddr != start_address) {
return -EINVAL;
}
if (!--act->refcnt) {
do_unmap(GINT_TO_POINTER(refs[0]), act, s);
g_hash_table_remove(xgt->active_maps, GINT_TO_POINTER(refs[0]));
}
return 0;
}
/*
* This looks a bit like the one for true Xen in xen-operations.c but
* in emulation we don't support multi-page mappings. And under Xen we
* *want* the multi-page mappings so we have fewer bounces through the
* kernel and the hypervisor. So the code paths end up being similar,
* but different.
*/
static int xen_be_gnttab_copy(struct xengntdev_handle *xgt, bool to_domain,
uint32_t domid, XenGrantCopySegment *segs,
uint32_t nr_segs, Error **errp)
{
int prot = to_domain ? PROT_WRITE : PROT_READ;
unsigned int i;
for (i = 0; i < nr_segs; i++) {
XenGrantCopySegment *seg = &segs[i];
void *page;
uint32_t ref = to_domain ? seg->dest.foreign.ref :
seg->source.foreign.ref;
page = xen_be_gnttab_map_refs(xgt, 1, domid, &ref, prot);
if (!page) {
if (errp) {
error_setg_errno(errp, errno,
"xen_be_gnttab_map_refs failed");
}
return -errno;
}
if (to_domain) {
memcpy(page + seg->dest.foreign.offset, seg->source.virt,
seg->len);
} else {
memcpy(seg->dest.virt, page + seg->source.foreign.offset,
seg->len);
}
if (xen_be_gnttab_unmap(xgt, page, &ref, 1)) {
if (errp) {
error_setg_errno(errp, errno, "xen_be_gnttab_unmap failed");
}
return -errno;
}
}
return 0;
}
static struct xengntdev_handle *xen_be_gnttab_open(void)
{
struct xengntdev_handle *xgt = g_new0(struct xengntdev_handle, 1);
xgt->active_maps = g_hash_table_new(g_direct_hash, g_direct_equal);
return xgt;
}
static int xen_be_gnttab_close(struct xengntdev_handle *xgt)
{
XenGnttabState *s = xen_gnttab_singleton;
if (!s) {
return -ENOTSUP;
}
g_hash_table_foreach_remove(xgt->active_maps, do_unmap, s);
g_hash_table_destroy(xgt->active_maps);
g_free(xgt);
return 0;
}
static struct gnttab_backend_ops emu_gnttab_backend_ops = {
.open = xen_be_gnttab_open,
.close = xen_be_gnttab_close,
.grant_copy = xen_be_gnttab_copy,
.set_max_grants = xen_be_gnttab_set_max_grants,
.map_refs = xen_be_gnttab_map_refs,
.unmap = xen_be_gnttab_unmap,
};
int xen_gnttab_reset(void)
{
XenGnttabState *s = xen_gnttab_singleton;
if (!s) {
return -ENOTSUP;
}
QEMU_LOCK_GUARD(&s->gnt_lock);
s->nr_frames = 0;
memset(s->entries.v1, 0, XEN_PAGE_SIZE * s->max_frames);
s->entries.v1[GNTTAB_RESERVED_XENSTORE].flags = GTF_permit_access;
s->entries.v1[GNTTAB_RESERVED_XENSTORE].frame = XEN_SPECIAL_PFN(XENSTORE);
if (xen_primary_console_get_pfn()) {
s->entries.v1[GNTTAB_RESERVED_CONSOLE].flags = GTF_permit_access;
s->entries.v1[GNTTAB_RESERVED_CONSOLE].frame = XEN_SPECIAL_PFN(CONSOLE);
}
return 0;
}