hostmem-memfd: preserve for cpr

Preserve memory-backend-memfd memory objects during cpr-transfer.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/1736967650-129648-10-git-send-email-steven.sistare@oracle.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>

backends/hostmem-memfd.c

@@ -17,6 +17,7 @@
 #include "qemu/module.h"
 #include "qapi/error.h"
 #include "qom/object.h"
+#include "migration/cpr.h"
 
 OBJECT_DECLARE_SIMPLE_TYPE(HostMemoryBackendMemfd, MEMORY_BACKEND_MEMFD)
 
@@ -33,15 +34,19 @@ static bool
 memfd_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
 {
     HostMemoryBackendMemfd *m = MEMORY_BACKEND_MEMFD(backend);
-    g_autofree char *name = NULL;
+    g_autofree char *name = host_memory_backend_get_name(backend);
+    int fd = cpr_find_fd(name, 0);
     uint32_t ram_flags;
-    int fd;
 
     if (!backend->size) {
         error_setg(errp, "can't create backend with size 0");
         return false;
     }
 
+    if (fd >= 0) {
+        goto have_fd;
+    }
+
     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,
@@ -49,9 +54,10 @@ memfd_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
     if (fd == -1) {
         return false;
     }
+    cpr_save_fd(name, 0, fd);
 
+have_fd:
     backend->aligned = true;
-    name = host_memory_backend_get_name(backend);
     ram_flags = backend->share ? RAM_SHARED : RAM_PRIVATE;
     ram_flags |= backend->reserve ? 0 : RAM_NORESERVE;
     ram_flags |= backend->guest_memfd ? RAM_GUEST_MEMFD : 0;