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/*
* QEMU host POSIX shared memory object backend
*
* Copyright (C) 2024 Red Hat Inc
*
* Authors:
* Stefano Garzarella <sgarzare@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 "system/hostmem.h"
#include "qapi/error.h"
#include "migration/cpr.h"
#define TYPE_MEMORY_BACKEND_SHM "memory-backend-shm"
OBJECT_DECLARE_SIMPLE_TYPE(HostMemoryBackendShm, MEMORY_BACKEND_SHM)
struct HostMemoryBackendShm {
HostMemoryBackend parent_obj;
};
static bool
shm_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
{
g_autofree char *backend_name = host_memory_backend_get_name(backend);
uint32_t ram_flags;
int fd = cpr_find_fd(backend_name, 0);
if (!backend->size) {
error_setg(errp, "can't create shm backend with size 0");
return false;
}
if (!backend->share) {
error_setg(errp, "can't create shm backend with `share=off`");
return false;
}
if (fd >= 0) {
goto have_fd;
}
fd = qemu_shm_alloc(backend->size, errp);
if (fd < 0) {
return false;
}
cpr_save_fd(backend_name, 0, fd);
have_fd:
/* Let's do the same as memory-backend-ram,share=on would do. */
ram_flags = RAM_SHARED;
ram_flags |= backend->reserve ? 0 : RAM_NORESERVE;
return memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend),
backend_name, backend->size,
ram_flags, fd, 0, errp);
}
static void
shm_backend_instance_init(Object *obj)
{
HostMemoryBackendShm *m = MEMORY_BACKEND_SHM(obj);
MEMORY_BACKEND(m)->share = true;
}
static void
shm_backend_class_init(ObjectClass *oc, void *data)
{
HostMemoryBackendClass *bc = MEMORY_BACKEND_CLASS(oc);
bc->alloc = shm_backend_memory_alloc;
}
static const TypeInfo shm_backend_info = {
.name = TYPE_MEMORY_BACKEND_SHM,
.parent = TYPE_MEMORY_BACKEND,
.instance_init = shm_backend_instance_init,
.class_init = shm_backend_class_init,
.instance_size = sizeof(HostMemoryBackendShm),
};
static void register_types(void)
{
type_register_static(&shm_backend_info);
}
type_init(register_types);
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