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hostmem-memfd-private.c
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hostmem-memfd-private.c
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/*
* QEMU host private memfd memory backend
*
* Copyright (C) 2021 Intel Corporation
*
* Authors:
* Chao Peng <chao.p.peng@linux.intel.com>
*
* 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 "sysemu/hostmem.h"
#include "hw/boards.h"
#include "qom/object_interfaces.h"
#include "qemu/memfd.h"
#include "qemu/module.h"
#include "qemu/units.h"
#include "qapi/error.h"
#include "qom/object.h"
#include "exec/confidential-guest-support.h"
#define MIN_DISCARD_SZ 4096
struct HostMemoryBackendPrivateMemfd {
HostMemoryBackend parent_obj;
bool hugetlb;
uint64_t hugetlbsize;
unsigned long *discard_bitmap;
int64_t discard_bitmap_size;
QLIST_HEAD(, RamDiscardListener) rdl_list;
};
static void
priv_memfd_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
{
HostMemoryBackendPrivateMemfd *m = MEMORY_BACKEND_MEMFD_PRIVATE(backend);
MachineState *machine = MACHINE(qdev_get_machine());
ConfidentialGuestSupport *cgs = machine->cgs;
Error *local_err = NULL;
uint32_t ram_flags;
char *name;
int fd;
if (!backend->size) {
error_setg(errp, "can't create backend with size 0");
return;
}
fd = qemu_memfd_create("memory-backend-memfd-shared", backend->size,
m->hugetlb, m->hugetlbsize, 0, errp);
if (fd == -1) {
return;
}
name = host_memory_backend_get_name(backend);
ram_flags = backend->share ? RAM_SHARED : 0;
ram_flags |= backend->reserve ? 0 : RAM_NORESERVE;
memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend), name,
backend->size, ram_flags, fd, 0, errp);
g_free(name);
memory_region_set_restricted_fd(&backend->mr, backend->size, &local_err);
if (local_err) {
error_propagate(errp, local_err);
return;
}
machine->ram_size = backend->size;
#define DISCARD_NONE 3
if (cgs->discard != DISCARD_NONE) {
g_warning("Registering RAM discard manager for private memfd backend.");
m->discard_bitmap_size = backend->size / MIN_DISCARD_SZ;
m->discard_bitmap = bitmap_new(m->discard_bitmap_size);
memory_region_set_ram_discard_manager(host_memory_backend_get_memory(backend),
RAM_DISCARD_MANAGER(m));
}
}
static bool
priv_memfd_backend_get_hugetlb(Object *o, Error **errp)
{
return MEMORY_BACKEND_MEMFD_PRIVATE(o)->hugetlb;
}
static void
priv_memfd_backend_set_hugetlb(Object *o, bool value, Error **errp)
{
MEMORY_BACKEND_MEMFD_PRIVATE(o)->hugetlb = value;
}
static void
priv_memfd_backend_set_hugetlbsize(Object *obj, Visitor *v, const char *name,
void *opaque, Error **errp)
{
HostMemoryBackendPrivateMemfd *m = MEMORY_BACKEND_MEMFD_PRIVATE(obj);
uint64_t value;
if (host_memory_backend_mr_inited(MEMORY_BACKEND(obj))) {
error_setg(errp, "cannot change property value");
return;
}
if (!visit_type_size(v, name, &value, errp)) {
return;
}
if (!value) {
error_setg(errp, "Property '%s.%s' doesn't take value '%" PRIu64 "'",
object_get_typename(obj), name, value);
return;
}
m->hugetlbsize = value;
}
static void
priv_memfd_backend_get_hugetlbsize(Object *obj, Visitor *v, const char *name,
void *opaque, Error **errp)
{
HostMemoryBackendPrivateMemfd *m = MEMORY_BACKEND_MEMFD_PRIVATE(obj);
uint64_t value = m->hugetlbsize;
visit_type_size(v, name, &value, errp);
}
static void
priv_memfd_backend_instance_init(Object *obj)
{
HostMemoryBackendPrivateMemfd *m = MEMORY_BACKEND_MEMFD_PRIVATE(obj);
MEMORY_BACKEND(obj)->reserve = false;
QLIST_INIT(&m->rdl_list);
}
static uint64_t priv_memfd_rdm_get_min_granularity(const RamDiscardManager *rdm,
const MemoryRegion *mr)
{
return MIN_DISCARD_SZ;
}
static bool priv_memfd_rdm_is_populated(const RamDiscardManager *rdm,
const MemoryRegionSection *s)
{
const HostMemoryBackendPrivateMemfd *m = MEMORY_BACKEND_MEMFD_PRIVATE(rdm);
const unsigned long first_bit = s->offset_within_region / MIN_DISCARD_SZ;
const unsigned long last_bit = first_bit + int128_get64(s->size) / MIN_DISCARD_SZ;
unsigned long first_populated_bit;
first_populated_bit = find_next_zero_bit(m->discard_bitmap, last_bit + 1,
first_bit);
return first_populated_bit > last_bit;
}
static bool priv_memfd_rdm_find_intersect(const HostMemoryBackendPrivateMemfd *m,
MemoryRegionSection *s,
uint64_t offset, uint64_t size)
{
uint64_t start = MAX(s->offset_within_region, offset);
uint64_t end = MIN(s->offset_within_region + int128_get64(s->size),
offset + size);
if (end <= start) {
return false;
}
s->offset_within_address_space += start - s->offset_within_region;
s->offset_within_region = start;
s->size = int128_make64(end - start);
return true;
}
typedef int (*priv_memfd_section_cb)(MemoryRegionSection *s, void *arg);
static int priv_memfd_notify_populate_cb(MemoryRegionSection *s, void *arg)
{
RamDiscardListener *rdl = arg;
return rdl->notify_populate(rdl, s);
}
static int priv_memfd_notify_discard_cb(MemoryRegionSection *s, void *arg)
{
RamDiscardListener *rdl = arg;
rdl->notify_discard(rdl, s);
return 0;
}
static int priv_memfd_for_each_populated_range(const HostMemoryBackendPrivateMemfd *m,
MemoryRegionSection *s,
void *arg,
priv_memfd_section_cb cb)
{
unsigned long first_zero_bit, last_zero_bit;
int ret;
first_zero_bit = find_first_zero_bit(m->discard_bitmap,
m->discard_bitmap_size);
while (first_zero_bit < m->discard_bitmap_size) {
MemoryRegionSection tmp = *s;
uint64_t offset, size;
offset = first_zero_bit * MIN_DISCARD_SZ;
last_zero_bit = find_next_bit(m->discard_bitmap, m->discard_bitmap_size,
first_zero_bit + 1) - 1;
size = (last_zero_bit - first_zero_bit + 1) * MIN_DISCARD_SZ;
if (!priv_memfd_rdm_find_intersect(m, &tmp, offset, size)) {
break;
}
ret = cb(&tmp, arg);
if (ret) {
break;
}
first_zero_bit = find_next_zero_bit(m->discard_bitmap,
m->discard_bitmap_size,
last_zero_bit + 2);
}
return false;
}
static int priv_memfd_for_each_discarded_range(const HostMemoryBackendPrivateMemfd *m,
MemoryRegionSection *s,
void *arg,
priv_memfd_section_cb cb)
{
unsigned long first_bit, last_bit;
int ret;
first_bit = find_first_bit(m->discard_bitmap, m->discard_bitmap_size);
while (first_bit < m->discard_bitmap_size) {
MemoryRegionSection tmp = *s;
uint64_t offset, size;
offset = first_bit * MIN_DISCARD_SZ;
last_bit = find_next_zero_bit(m->discard_bitmap, m->discard_bitmap_size,
first_bit + 1) - 1;
size = (last_bit - first_bit + 1) * MIN_DISCARD_SZ;
if (!priv_memfd_rdm_find_intersect(m, &tmp, offset, size)) {
break;
}
ret = cb(&tmp, arg);
if (ret) {
break;
}
first_bit = find_next_bit(m->discard_bitmap,
m->discard_bitmap_size, last_bit + 2);
}
return false;
}
typedef struct PrivateMemfdReplayData {
void *fn;
void *opaque;
} PrivateMemfdReplayData;
static int priv_memfd_rdm_replay_populated_cb(MemoryRegionSection *s, void *arg)
{
PrivateMemfdReplayData *data = arg;
return ((ReplayRamPopulate)data->fn)(s, data->opaque);
}
static int priv_memfd_rdm_replay_populated(const RamDiscardManager *rdm,
MemoryRegionSection *s,
ReplayRamPopulate replay_fn,
void *opaque)
{
const HostMemoryBackendPrivateMemfd *m = MEMORY_BACKEND_MEMFD_PRIVATE(rdm);
struct PrivateMemfdReplayData data = {
.fn = replay_fn,
.opaque = opaque,
};
g_assert(s->mr == host_memory_backend_get_memory(MEMORY_BACKEND(m)));
return priv_memfd_for_each_populated_range(m, s, &data,
priv_memfd_rdm_replay_populated_cb);
}
static int priv_memfd_rdm_replay_discarded_cb(MemoryRegionSection *s, void *arg)
{
PrivateMemfdReplayData *data = arg;
return ((ReplayRamPopulate)data->fn)(s, data->opaque);
}
static void priv_memfd_rdm_replay_discarded(const RamDiscardManager *rdm,
MemoryRegionSection *s,
ReplayRamDiscard replay_fn,
void *opaque)
{
const HostMemoryBackendPrivateMemfd *m = MEMORY_BACKEND_MEMFD_PRIVATE(rdm);
struct PrivateMemfdReplayData data = {
.fn = replay_fn,
.opaque = opaque,
};
g_assert(s->mr == host_memory_backend_get_memory(MEMORY_BACKEND(m)));
priv_memfd_for_each_discarded_range(m, s, &data,
priv_memfd_rdm_replay_discarded_cb);
}
static void priv_memfd_rdm_register_listener(RamDiscardManager *rdm,
RamDiscardListener *rdl,
MemoryRegionSection *s)
{
HostMemoryBackendPrivateMemfd *m = MEMORY_BACKEND_MEMFD_PRIVATE(rdm);
int ret;
g_assert(s->mr == host_memory_backend_get_memory(MEMORY_BACKEND(m)));
rdl->section = memory_region_section_new_copy(s);
QLIST_INSERT_HEAD(&m->rdl_list, rdl, next);
ret = priv_memfd_for_each_populated_range(m, s, rdl, priv_memfd_notify_populate_cb);
if (ret) {
g_warning("failed to register RAM discard listener: %d", ret);
return;
}
}
static void priv_memfd_rdm_unregister_listener(RamDiscardManager *rdm,
RamDiscardListener *rdl)
{
HostMemoryBackendPrivateMemfd *m = MEMORY_BACKEND_MEMFD_PRIVATE(rdm);
int ret;
g_assert(rdl->section->mr == host_memory_backend_get_memory(MEMORY_BACKEND(m)));
ret = priv_memfd_for_each_populated_range(m, rdl->section, rdl, priv_memfd_notify_discard_cb);
if (ret) {
g_warning("failed to unregister RAM discard listener: %d", ret);
return;
}
memory_region_section_free_copy(rdl->section);
rdl->section = NULL;
QLIST_REMOVE(rdl, next);
}
static int priv_memfd_discard(Object *backend, RAMBlock *rb, uint64_t offset, uint64_t size, bool shared_to_private)
{
HostMemoryBackendPrivateMemfd *m = MEMORY_BACKEND_MEMFD_PRIVATE(backend);
RamDiscardListener *rdl, *rdl2;
int ret = 0;
assert((size % MIN_DISCARD_SZ) == 0);
QLIST_FOREACH(rdl, &m->rdl_list, next) {
MemoryRegionSection tmp = *rdl->section;
if (!priv_memfd_rdm_find_intersect(m, &tmp, offset, size)) {
continue;
}
if (shared_to_private) {
rdl->notify_discard(rdl, &tmp);
} else {
ret = rdl->notify_populate(rdl, &tmp);
}
if (ret) {
break;
}
}
if (!ret) {
const unsigned long first_bit = offset / MIN_DISCARD_SZ;
const unsigned long nbits = size / MIN_DISCARD_SZ;
assert((first_bit + nbits) <= m->discard_bitmap_size);
ret = ram_block_convert_range(rb, offset, size, shared_to_private);
if (ret) {
goto rollback;
}
if (shared_to_private) {
bitmap_set(m->discard_bitmap, first_bit, nbits);
} else {
bitmap_clear(m->discard_bitmap, first_bit, nbits);
}
return 0;
}
rollback:
/* Something went wrong, roll back listener updates. */
QLIST_FOREACH(rdl2, &m->rdl_list, next) {
MemoryRegionSection tmp = *rdl2->section;
if (rdl2 == rdl) {
break;
}
if (!priv_memfd_rdm_find_intersect(m, &tmp, offset, size)) {
continue;
}
if (shared_to_private) {
rdl2->notify_populate(rdl, &tmp);
} else {
rdl2->notify_discard(rdl, &tmp);
}
}
return ret;
}
static void
priv_memfd_backend_class_init(ObjectClass *oc, void *data)
{
HostMemoryBackendClass *bc = MEMORY_BACKEND_CLASS(oc);
HostMemoryBackendPrivateMemfdClass *pbc = MEMORY_BACKEND_MEMFD_PRIVATE_CLASS(bc);
RamDiscardManagerClass *rdmc = RAM_DISCARD_MANAGER_CLASS(pbc);
bc->alloc = priv_memfd_backend_memory_alloc;
pbc->discard = priv_memfd_discard;
if (qemu_memfd_check(MFD_HUGETLB)) {
object_class_property_add_bool(oc, "hugetlb",
priv_memfd_backend_get_hugetlb,
priv_memfd_backend_set_hugetlb);
object_class_property_set_description(oc, "hugetlb",
"Use huge pages");
object_class_property_add(oc, "hugetlbsize", "int",
priv_memfd_backend_get_hugetlbsize,
priv_memfd_backend_set_hugetlbsize,
NULL, NULL);
object_class_property_set_description(oc, "hugetlbsize",
"Huge pages size (ex: 2M, 1G)");
}
rdmc->get_min_granularity = priv_memfd_rdm_get_min_granularity;
rdmc->is_populated = priv_memfd_rdm_is_populated;
rdmc->replay_populated = priv_memfd_rdm_replay_populated;
rdmc->replay_discarded = priv_memfd_rdm_replay_discarded;
rdmc->register_listener = priv_memfd_rdm_register_listener;
rdmc->unregister_listener = priv_memfd_rdm_unregister_listener;
}
static const TypeInfo priv_memfd_backend_info = {
.name = TYPE_MEMORY_BACKEND_MEMFD_PRIVATE,
.parent = TYPE_MEMORY_BACKEND,
.instance_init = priv_memfd_backend_instance_init,
.class_init = priv_memfd_backend_class_init,
.instance_size = sizeof(HostMemoryBackendPrivateMemfd),
.interfaces = (InterfaceInfo[]) {
{ TYPE_RAM_DISCARD_MANAGER },
{ }
},
};
static void register_types(void)
{
if (qemu_memfd_check(MFD_ALLOW_SEALING)) {
type_register_static(&priv_memfd_backend_info);
}
}
type_init(register_types);