qemu/backends/hostmem-memfd.c
Igor Mammedov 4ebc74dbbf hostmem: fix strict bind policy
When option -mem-prealloc is used with one or more memory-backend
objects, created backends may not obey configured bind policy or
creation may fail after kernel attempts to move pages according
to bind policy.
Reason is in file_ram_alloc(), which will pre-allocate
any descriptor based RAM if global mem_prealloc != 0 and that
happens way before bind policy is applied to memory range.

One way to fix it would be to extend memory_region_foo() API
and add more invariants that could broken later due implicit
dependencies that's hard to track.

Another approach is to drop adhoc main RAM allocation and
consolidate it around memory-backend. That allows to have
single place that allocates guest RAM (main and memdev)
in the same way and then global mem_prealloc could be
replaced by backend's property[s] that will affect created
memory-backend objects but only in correct order this time.

With main RAM now converted to hostmem backends, there is no
point in keeping global mem_prealloc around, so alias
 -mem-prealloc to "memory-backend.prealloc=on"
machine compat[*] property and make mem_prealloc a local
variable to only stir registration of compat property.

*) currently user accessible -global works only with DEVICE
   based objects and extra work is needed to make it work
   with hostmem backends. But that is convenience option
   and out of scope of this already huge refactoring.
   Hence machine compat properties were used.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20200219160953.13771-78-imammedo@redhat.com>
2020-02-19 16:50:02 +00:00

182 lines
5.2 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 "sysemu/sysemu.h"
#include "qom/object_interfaces.h"
#include "qemu/memfd.h"
#include "qemu/module.h"
#include "qapi/error.h"
#define TYPE_MEMORY_BACKEND_MEMFD "memory-backend-memfd"
#define MEMORY_BACKEND_MEMFD(obj) \
OBJECT_CHECK(HostMemoryBackendMemfd, (obj), TYPE_MEMORY_BACKEND_MEMFD)
typedef struct HostMemoryBackendMemfd HostMemoryBackendMemfd;
struct HostMemoryBackendMemfd {
HostMemoryBackend parent_obj;
bool hugetlb;
uint64_t hugetlbsize;
bool seal;
};
static void
memfd_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
{
HostMemoryBackendMemfd *m = MEMORY_BACKEND_MEMFD(backend);
char *name;
int fd;
if (!backend->size) {
error_setg(errp, "can't create backend with size 0");
return;
}
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;
}
name = host_memory_backend_get_name(backend);
memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend),
name, backend->size,
backend->share, fd, errp);
g_free(name);
}
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);
Error *local_err = NULL;
uint64_t value;
if (host_memory_backend_mr_inited(MEMORY_BACKEND(obj))) {
error_setg(&local_err, "cannot change property value");
goto out;
}
visit_type_size(v, name, &value, &local_err);
if (local_err) {
goto out;
}
if (!value) {
error_setg(&local_err, "Property '%s.%s' doesn't take value '%"
PRIu64 "'", object_get_typename(obj), name, value);
goto out;
}
m->hugetlbsize = value;
out:
error_propagate(errp, local_err);
}
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,
&error_abort);
object_class_property_set_description(oc, "hugetlb",
"Use huge pages",
&error_abort);
object_class_property_add(oc, "hugetlbsize", "int",
memfd_backend_get_hugetlbsize,
memfd_backend_set_hugetlbsize,
NULL, NULL, &error_abort);
object_class_property_set_description(oc, "hugetlbsize",
"Huge pages size (ex: 2M, 1G)",
&error_abort);
}
object_class_property_add_bool(oc, "seal",
memfd_backend_get_seal,
memfd_backend_set_seal,
&error_abort);
object_class_property_set_description(oc, "seal",
"Seal growing & shrinking",
&error_abort);
}
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);