qemu/backends/hostmem-memfd.c
Michal Privoznik 5d9a9a6170 backends/hostmem: Report error when memory size is unaligned
If memory-backend-{file,ram} has a size that's not aligned to
underlying page size it is not only wasteful, but also may lead
to hard to debug behaviour. For instance, in case
memory-backend-file and hugepages, madvise() and mbind() fail.
Rightfully so, page is the smallest unit they can work with. And
even though an error is reported, the root cause it not very
clear:

  qemu-system-x86_64: Couldn't set property 'dump' on 'memory-backend-file': Invalid argument

After this commit:

  qemu-system-x86_64: backend 'memory-backend-file' memory size must be multiple of 2 MiB

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Mario Casquero <mcasquer@redhat.com>
Message-ID: <b5b9f9c6bba07879fb43f3c6f496c69867ae3716.1717584048.git.mprivozn@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-06-08 10:33:38 +02:00

174 lines
4.9 KiB
C

/*
* QEMU host memfd memory backend
*
* Copyright (C) 2018 Red Hat Inc
*
* Authors:
* Marc-André Lureau <marcandre.lureau@redhat.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 "qom/object_interfaces.h"
#include "qemu/memfd.h"
#include "qemu/module.h"
#include "qapi/error.h"
#include "qom/object.h"
#define TYPE_MEMORY_BACKEND_MEMFD "memory-backend-memfd"
OBJECT_DECLARE_SIMPLE_TYPE(HostMemoryBackendMemfd, MEMORY_BACKEND_MEMFD)
struct HostMemoryBackendMemfd {
HostMemoryBackend parent_obj;
bool hugetlb;
uint64_t hugetlbsize;
bool seal;
};
static bool
memfd_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
{
HostMemoryBackendMemfd *m = MEMORY_BACKEND_MEMFD(backend);
g_autofree char *name = NULL;
uint32_t ram_flags;
int fd;
if (!backend->size) {
error_setg(errp, "can't create backend with size 0");
return false;
}
fd = qemu_memfd_create(TYPE_MEMORY_BACKEND_MEMFD, backend->size,
m->hugetlb, m->hugetlbsize, m->seal ?
F_SEAL_GROW | F_SEAL_SHRINK | F_SEAL_SEAL : 0,
errp);
if (fd == -1) {
return false;
}
backend->aligned = true;
name = host_memory_backend_get_name(backend);
ram_flags = backend->share ? RAM_SHARED : 0;
ram_flags |= backend->reserve ? 0 : RAM_NORESERVE;
ram_flags |= backend->guest_memfd ? RAM_GUEST_MEMFD : 0;
return memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend), name,
backend->size, ram_flags, fd, 0, errp);
}
static bool
memfd_backend_get_hugetlb(Object *o, Error **errp)
{
return MEMORY_BACKEND_MEMFD(o)->hugetlb;
}
static void
memfd_backend_set_hugetlb(Object *o, bool value, Error **errp)
{
MEMORY_BACKEND_MEMFD(o)->hugetlb = value;
}
static void
memfd_backend_set_hugetlbsize(Object *obj, Visitor *v, const char *name,
void *opaque, Error **errp)
{
HostMemoryBackendMemfd *m = MEMORY_BACKEND_MEMFD(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
memfd_backend_get_hugetlbsize(Object *obj, Visitor *v, const char *name,
void *opaque, Error **errp)
{
HostMemoryBackendMemfd *m = MEMORY_BACKEND_MEMFD(obj);
uint64_t value = m->hugetlbsize;
visit_type_size(v, name, &value, errp);
}
static bool
memfd_backend_get_seal(Object *o, Error **errp)
{
return MEMORY_BACKEND_MEMFD(o)->seal;
}
static void
memfd_backend_set_seal(Object *o, bool value, Error **errp)
{
MEMORY_BACKEND_MEMFD(o)->seal = value;
}
static void
memfd_backend_instance_init(Object *obj)
{
HostMemoryBackendMemfd *m = MEMORY_BACKEND_MEMFD(obj);
/* default to sealed file */
m->seal = true;
MEMORY_BACKEND(m)->share = true;
}
static void
memfd_backend_class_init(ObjectClass *oc, void *data)
{
HostMemoryBackendClass *bc = MEMORY_BACKEND_CLASS(oc);
bc->alloc = memfd_backend_memory_alloc;
if (qemu_memfd_check(MFD_HUGETLB)) {
object_class_property_add_bool(oc, "hugetlb",
memfd_backend_get_hugetlb,
memfd_backend_set_hugetlb);
object_class_property_set_description(oc, "hugetlb",
"Use huge pages");
object_class_property_add(oc, "hugetlbsize", "int",
memfd_backend_get_hugetlbsize,
memfd_backend_set_hugetlbsize,
NULL, NULL);
object_class_property_set_description(oc, "hugetlbsize",
"Huge pages size (ex: 2M, 1G)");
}
object_class_property_add_bool(oc, "seal",
memfd_backend_get_seal,
memfd_backend_set_seal);
object_class_property_set_description(oc, "seal",
"Seal growing & shrinking");
}
static const TypeInfo memfd_backend_info = {
.name = TYPE_MEMORY_BACKEND_MEMFD,
.parent = TYPE_MEMORY_BACKEND,
.instance_init = memfd_backend_instance_init,
.class_init = memfd_backend_class_init,
.instance_size = sizeof(HostMemoryBackendMemfd),
};
static void register_types(void)
{
if (qemu_memfd_check(MFD_ALLOW_SEALING)) {
type_register_static(&memfd_backend_info);
}
}
type_init(register_types);