diff --git a/block-Fix-cross-AioContext-blockdev-snapshot.patch b/block-Fix-cross-AioContext-blockdev-snapshot.patch
new file mode 100644
index 0000000..a4a4d9d
--- /dev/null
+++ b/block-Fix-cross-AioContext-blockdev-snapshot.patch
@@ -0,0 +1,78 @@
+From ec96b9f64c239736003413d70dc3999ad0b8271c Mon Sep 17 00:00:00 2001
+From: Kevin Wolf <kwolf@redhat.com>
+Date: Tue, 10 Mar 2020 12:38:29 +0100
+Subject: [PATCH] block: Fix cross-AioContext blockdev-snapshot
+
+external_snapshot_prepare() tries to move the overlay to the AioContext
+of the backing file (the snapshotted node). However, it's possible that
+this doesn't work, but the backing file can instead be moved to the
+overlay's AioContext (e.g. opening the backing chain for a mirror
+target).
+
+bdrv_append() already indirectly uses bdrv_attach_node(), which takes
+care to move nodes to make sure they use the same AioContext and which
+tries both directions.
+
+So the problem has a simple fix: Just delete the unnecessary extra
+bdrv_try_set_aio_context() call in external_snapshot_prepare() and
+instead assert in bdrv_append() that both nodes were indeed moved to the
+same AioContext.
+
+Signed-off-by: Kevin Wolf <kwolf@redhat.com>
+Message-Id: <20200310113831.27293-6-kwolf@redhat.com>
+Tested-by: Peter Krempa <pkrempa@redhat.com>
+Signed-off-by: Kevin Wolf <kwolf@redhat.com>
+---
+ block.c    |  1 +
+ blockdev.c | 16 ----------------
+ 2 files changed, 1 insertion(+), 16 deletions(-)
+
+diff --git a/block.c b/block.c
+index ba36b53a00..824025f781 100644
+--- a/block.c
++++ b/block.c
+@@ -4165,6 +4165,7 @@ void bdrv_replace_node(BlockDriverState *from, BlockDriverState *to,
+     bdrv_ref(from);
+ 
+     assert(qemu_get_current_aio_context() == qemu_get_aio_context());
++    assert(bdrv_get_aio_context(from) == bdrv_get_aio_context(to));
+     bdrv_drained_begin(from);
+ 
+     /* Put all parents into @list and calculate their cumulative permissions */
+diff --git a/blockdev.c b/blockdev.c
+index 79112be2e6..d1a3b6a630 100644
+--- a/blockdev.c
++++ b/blockdev.c
+@@ -1578,8 +1578,6 @@ static void external_snapshot_prepare(BlkActionState *common,
+                              DO_UPCAST(ExternalSnapshotState, common, common);
+     TransactionAction *action = common->action;
+     AioContext *aio_context;
+-    AioContext *old_context;
+-    int ret;
+ 
+     /* 'blockdev-snapshot' and 'blockdev-snapshot-sync' have similar
+      * purpose but a different set of parameters */
+@@ -1719,20 +1717,6 @@ static void external_snapshot_prepare(BlkActionState *common,
+         goto out;
+     }
+ 
+-    /* Honor bdrv_try_set_aio_context() context acquisition requirements. */
+-    old_context = bdrv_get_aio_context(state->new_bs);
+-    aio_context_release(aio_context);
+-    aio_context_acquire(old_context);
+-
+-    ret = bdrv_try_set_aio_context(state->new_bs, aio_context, errp);
+-
+-    aio_context_release(old_context);
+-    aio_context_acquire(aio_context);
+-
+-    if (ret < 0) {
+-        goto out;
+-    }
+-
+     /* This removes our old bs and adds the new bs. This is an operation that
+      * can fail, so we need to do it in .prepare; undoing it for abort is
+      * always possible. */
+-- 
+2.27.0
+