block: add BlockRAMRegistrar
Emulated devices and other BlockBackend users wishing to take advantage
of blk_register_buf() all have the same repetitive job: register
RAMBlocks with the BlockBackend using RAMBlockNotifier.
Add a BlockRAMRegistrar API to do this. A later commit will use this
from hw/block/virtio-blk.c.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20221013185908.1297568-10-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/block/block-ram-registrar.c b/block/block-ram-registrar.c
new file mode 100644
index 0000000..25dbafa
--- /dev/null
+++ b/block/block-ram-registrar.c
@@ -0,0 +1,58 @@
+/*
+ * BlockBackend RAM Registrar
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "sysemu/block-backend.h"
+#include "sysemu/block-ram-registrar.h"
+#include "qapi/error.h"
+
+static void ram_block_added(RAMBlockNotifier *n, void *host, size_t size,
+ size_t max_size)
+{
+ BlockRAMRegistrar *r = container_of(n, BlockRAMRegistrar, notifier);
+ Error *err = NULL;
+
+ if (!r->ok) {
+ return; /* don't try again if we've already failed */
+ }
+
+ if (!blk_register_buf(r->blk, host, max_size, &err)) {
+ error_report_err(err);
+ ram_block_notifier_remove(&r->notifier);
+ r->ok = false;
+ }
+}
+
+static void ram_block_removed(RAMBlockNotifier *n, void *host, size_t size,
+ size_t max_size)
+{
+ BlockRAMRegistrar *r = container_of(n, BlockRAMRegistrar, notifier);
+ blk_unregister_buf(r->blk, host, max_size);
+}
+
+void blk_ram_registrar_init(BlockRAMRegistrar *r, BlockBackend *blk)
+{
+ r->blk = blk;
+ r->notifier = (RAMBlockNotifier){
+ .ram_block_added = ram_block_added,
+ .ram_block_removed = ram_block_removed,
+
+ /*
+ * .ram_block_resized() is not necessary because we use the max_size
+ * value that does not change across resize.
+ */
+ };
+ r->ok = true;
+
+ ram_block_notifier_add(&r->notifier);
+}
+
+void blk_ram_registrar_destroy(BlockRAMRegistrar *r)
+{
+ if (r->ok) {
+ ram_block_notifier_remove(&r->notifier);
+ }
+}
