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;
}
if (host_memory_backend_mr_inited(backend)) {
return;
}
backend->force_prealloc = mem_prealloc;
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 = object_get_canonical_path(OBJECT(backend));
memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend),
name, backend->size, true, fd, errp);
g_free(name);
}
/*
* This is a best-effort helper for shared memory allocation, with
* optional sealing. The helper will do his best to allocate using
* memfd with sealing, but may fallback on other methods without
* sealing.
*/
void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
int *fd, Error **errp)
{
void *ptr;
int mfd = qemu_memfd_create(name, size, false, 0, seals, NULL);
/* some systems have memfd without sealing */
if (mfd == -1) {
mfd = qemu_memfd_create(name, size, false, 0, 0, NULL);
}
if (mfd == -1) {
const char *tmpdir = g_get_tmp_dir();
gchar *fname;
fname = g_strdup_printf("%s/memfd-XXXXXX", tmpdir);
mfd = mkstemp(fname);
unlink(fname);
g_free(fname);
if (mfd == -1 ||
ftruncate(mfd, size) == -1) {
goto err;
}
}
ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
if (ptr == MAP_FAILED) {
goto err;
}
*fd = mfd;
return ptr;
err:
error_setg_errno(errp, errno, "failed to allocate shared memory");
if (mfd >= 0) {
close(mfd);
}
return NULL;
}
