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From 714d313805542063ea68e26a0d47b5059ee9952e Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Tue, 13 Aug 2013 09:06:36 +0200
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Subject: dataplane: enable virtio-blk x-data-plane=on live migration
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RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
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Message-id: <1376384797-4701-6-git-send-email-stefanha@redhat.com>
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Patchwork-id: 53210
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O-Subject: [PATCH v2 5/6] dataplane: enable virtio-blk x-data-plane=on live migration
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Bugzilla: 995030
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
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Although the dataplane thread does not cooperate with dirty memory
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logging yet it's fairly easy to temporarily disable dataplane during
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live migration.  This way virtio-blk can live migrate when
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x-data-plane=on.
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The dataplane thread will restart after migration is cancelled or if the
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guest resuming virtio-blk operation after migration completes.
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Reviewed-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit 84db52d059f3296abf7783968645c4a96d21b099)
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
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index 2faed43..63c3ffa 100644
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--- a/hw/block/dataplane/virtio-blk.c
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+++ b/hw/block/dataplane/virtio-blk.c
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@@ -18,7 +18,6 @@
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 #include "qemu/error-report.h"
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 #include "hw/virtio/dataplane/vring.h"
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 #include "ioq.h"
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-#include "migration/migration.h"
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 #include "block/block.h"
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 #include "hw/virtio/virtio-blk.h"
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 #include "virtio-blk.h"
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@@ -69,8 +68,6 @@ struct VirtIOBlockDataPlane {
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                                              queue */
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     unsigned int num_reqs;
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-
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-    Error *migration_blocker;
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 };
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 /* Raise an interrupt to signal guest, if necessary */
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@@ -433,10 +430,6 @@ bool virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
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     /* Prevent block operations that conflict with data plane thread */
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     bdrv_set_in_use(blk->conf.bs, 1);
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-    error_setg(&s->migration_blocker,
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-            "x-data-plane does not support migration");
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-    migrate_add_blocker(s->migration_blocker);
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-
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     *dataplane = s;
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     return true;
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 }
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@@ -448,8 +441,6 @@ void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
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     }
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     virtio_blk_data_plane_stop(s);
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-    migrate_del_blocker(s->migration_blocker);
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-    error_free(s->migration_blocker);
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     bdrv_set_in_use(s->blk->conf.bs, 0);
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     g_free(s);
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 }
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diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
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index cf12469..cca0c77 100644
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--- a/hw/block/virtio-blk.c
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+++ b/hw/block/virtio-blk.c
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@@ -19,6 +19,7 @@
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 #include "hw/virtio/virtio-blk.h"
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 #ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
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 # include "dataplane/virtio-blk.h"
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+# include "migration/migration.h"
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 #endif
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 #include "block/scsi.h"
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 #ifdef __linux__
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@@ -628,6 +629,34 @@ void virtio_blk_set_conf(DeviceState *dev, VirtIOBlkConf *blk)
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     memcpy(&(s->blk), blk, sizeof(struct VirtIOBlkConf));
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 }
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+#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
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+/* Disable dataplane thread during live migration since it does not
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+ * update the dirty memory bitmap yet.
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+ */
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+static void virtio_blk_migration_state_changed(Notifier *notifier, void *data)
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+{
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+    VirtIOBlock *s = container_of(notifier, VirtIOBlock,
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+                                  migration_state_notifier);
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+    MigrationState *mig = data;
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+
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+    if (migration_is_active(mig)) {
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+        if (!s->dataplane) {
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+            return;
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+        }
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+        virtio_blk_data_plane_destroy(s->dataplane);
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+        s->dataplane = NULL;
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+    } else if (migration_has_finished(mig) ||
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+               migration_has_failed(mig)) {
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+        if (s->dataplane) {
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+            return;
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+        }
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+        bdrv_drain_all(); /* complete in-flight non-dataplane requests */
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+        virtio_blk_data_plane_create(VIRTIO_DEVICE(s), &s->blk,
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+                                     &s->dataplane);
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+    }
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+}
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+#endif /* CONFIG_VIRTIO_BLK_DATA_PLANE */
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+
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 static int virtio_blk_device_init(VirtIODevice *vdev)
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 {
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     DeviceState *qdev = DEVICE(vdev);
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@@ -664,6 +693,8 @@ static int virtio_blk_device_init(VirtIODevice *vdev)
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         virtio_cleanup(vdev);
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         return -1;
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     }
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+    s->migration_state_notifier.notify = virtio_blk_migration_state_changed;
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+    add_migration_state_change_notifier(&s->migration_state_notifier);
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 #endif
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     s->change = qemu_add_vm_change_state_handler(virtio_blk_dma_restart_cb, s);
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@@ -683,6 +714,7 @@ static int virtio_blk_device_exit(DeviceState *dev)
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     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
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     VirtIOBlock *s = VIRTIO_BLK(dev);
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 #ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
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+    remove_migration_state_change_notifier(&s->migration_state_notifier);
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     virtio_blk_data_plane_destroy(s->dataplane);
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     s->dataplane = NULL;
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 #endif
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diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
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index fc71853..b87cf49 100644
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--- a/include/hw/virtio/virtio-blk.h
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+++ b/include/hw/virtio/virtio-blk.h
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@@ -125,6 +125,7 @@ typedef struct VirtIOBlock {
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     unsigned short sector_mask;
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     VMChangeStateEntry *change;
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 #ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
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+    Notifier migration_state_notifier;
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     struct VirtIOBlockDataPlane *dataplane;
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 #endif
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 } VirtIOBlock;