vhost-user-blk-server: notify client about disk resize

Currently block_resize qmp command is simply ignored by vhost-user-blk
export. So, the block-node is successfully resized, but virtio config
is unchanged and guest doesn't see that disk is resized.

Let's handle the resize by modifying the config and notifying the guest
appropriately.

After this comment, lsblk in linux guest with attached
vhost-user-blk-pci device shows new size immediately after block_resize
QMP command on vhost-user exported block node.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-Id: <20230321201323.3695923-1-vsementsov@yandex-team.ru>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/block/export/vhost-user-blk-server.c b/block/export/vhost-user-blk-server.c
index 3409d9e02e68bda491a985ea53eaf9fcac166b5d..e56b92f2e2bedfe5eb3fde44340b27c193006e0d 100644 (file)
--- a/block/export/vhost-user-blk-server.c
+++ b/block/export/vhost-user-blk-server.c
@@ -10,6 +10,7 @@
  * later.  See the COPYING file in the top-level directory.
  */
 #include "qemu/osdep.h"
+#include "qemu/error-report.h"
 #include "block/block.h"
 #include "subprojects/libvhost-user/libvhost-user.h" /* only for the type definitions */
 #include "standard-headers/linux/virtio_blk.h"
@@ -251,6 +252,27 @@ static void vu_blk_exp_request_shutdown(BlockExport *exp)
     vhost_user_server_stop(&vexp->vu_server);
 }
 
+static void vu_blk_exp_resize(void *opaque)
+{
+    VuBlkExport *vexp = opaque;
+    BlockDriverState *bs = blk_bs(vexp->handler.blk);
+    int64_t new_size = bdrv_getlength(bs);
+
+    if (new_size < 0) {
+        error_printf("Failed to get length of block node '%s'",
+                     bdrv_get_node_name(bs));
+        return;
+    }
+
+    vexp->blkcfg.capacity = cpu_to_le64(new_size >> VIRTIO_BLK_SECTOR_BITS);
+
+    vu_config_change_msg(&vexp->vu_server.vu_dev);
+}
+
+static const BlockDevOps vu_blk_dev_ops = {
+    .resize_cb = vu_blk_exp_resize,
+};
+
 static int vu_blk_exp_create(BlockExport *exp, BlockExportOptions *opts,
                              Error **errp)
 {
@@ -292,6 +314,8 @@ static int vu_blk_exp_create(BlockExport *exp, BlockExportOptions *opts,
     blk_add_aio_context_notifier(exp->blk, blk_aio_attached, blk_aio_detach,
                                  vexp);
 
+    blk_set_dev_ops(exp->blk, &vu_blk_dev_ops, vexp);
+
     if (!vhost_user_server_start(&vexp->vu_server, vu_opts->addr, exp->ctx,
                                  num_queues, &vu_blk_iface, errp)) {
         blk_remove_aio_context_notifier(exp->blk, blk_aio_attached,

diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
index 0200b78e8e1a1c18d53bc79afe6b806485a34f0b..0abd898a52c4cc6131743e51ac83ccc9a5819bce 100644 (file)
--- a/subprojects/libvhost-user/libvhost-user.c
+++ b/subprojects/libvhost-user/libvhost-user.c
@@ -2455,6 +2455,16 @@ void vu_queue_notify_sync(VuDev *dev, VuVirtq *vq)
     _vu_queue_notify(dev, vq, true);
 }
 
+void vu_config_change_msg(VuDev *dev)
+{
+    VhostUserMsg vmsg = {
+        .request = VHOST_USER_BACKEND_CONFIG_CHANGE_MSG,
+        .flags = VHOST_USER_VERSION,
+    };
+
+    vu_message_write(dev, dev->slave_fd, &vmsg);
+}
+
 static inline void
 vring_used_flags_set_bit(VuVirtq *vq, int mask)
 {

diff --git a/subprojects/libvhost-user/libvhost-user.h b/subprojects/libvhost-user/libvhost-user.h
index 8c5a2719e3693060ac33826ff9be77065e31159a..49208cceaaf2d7b5939792f756bbe9d6e6c604d5 100644 (file)
--- a/subprojects/libvhost-user/libvhost-user.h
+++ b/subprojects/libvhost-user/libvhost-user.h
@@ -585,6 +585,8 @@ bool vu_queue_empty(VuDev *dev, VuVirtq *vq);
  */
 void vu_queue_notify(VuDev *dev, VuVirtq *vq);
 
+void vu_config_change_msg(VuDev *dev);
+
 /**
  * vu_queue_notify_sync:
  * @dev: a VuDev context