Merge tag 'block-pull-request' of https://gitlab.com/stefanha/qemu into staging
Pull request
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# gpg: Signature made Wed 12 Jul 2023 08:33:49 PM BST
# gpg: using RSA key 8695A8BFD3F97CDAAC35775A9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg: aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
* tag 'block-pull-request' of https://gitlab.com/stefanha/qemu:
virtio-blk: fix host notifier issues during dataplane start/stop
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index c227b39..da36fcf 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -219,13 +219,6 @@
memory_region_transaction_commit();
- /*
- * These fields are visible to the IOThread so we rely on implicit barriers
- * in aio_context_acquire() on the write side and aio_notify_accept() on
- * the read side.
- */
- s->starting = false;
- vblk->dataplane_started = true;
trace_virtio_blk_data_plane_start(s);
old_context = blk_get_aio_context(s->conf->conf.blk);
@@ -244,6 +237,18 @@
event_notifier_set(virtio_queue_get_host_notifier(vq));
}
+ /*
+ * These fields must be visible to the IOThread when it processes the
+ * virtqueue, otherwise it will think dataplane has not started yet.
+ *
+ * Make sure ->dataplane_started is false when blk_set_aio_context() is
+ * called above so that draining does not cause the host notifier to be
+ * detached/attached prematurely.
+ */
+ s->starting = false;
+ vblk->dataplane_started = true;
+ smp_wmb(); /* paired with aio_notify_accept() on the read side */
+
/* Get this show started by hooking up our callbacks */
if (!blk_in_drain(s->conf->conf.blk)) {
aio_context_acquire(s->ctx);
@@ -273,7 +278,6 @@
fail_guest_notifiers:
vblk->dataplane_disabled = true;
s->starting = false;
- vblk->dataplane_started = true;
return -ENOSYS;
}
@@ -327,19 +331,6 @@
aio_wait_bh_oneshot(s->ctx, virtio_blk_data_plane_stop_bh, s);
}
- aio_context_acquire(s->ctx);
-
- /* Wait for virtio_blk_dma_restart_bh() and in flight I/O to complete */
- blk_drain(s->conf->conf.blk);
-
- /*
- * Try to switch bs back to the QEMU main loop. If other users keep the
- * BlockBackend in the iothread, that's ok
- */
- blk_set_aio_context(s->conf->conf.blk, qemu_get_aio_context(), NULL);
-
- aio_context_release(s->ctx);
-
/*
* Batch all the host notifiers in a single transaction to avoid
* quadratic time complexity in address_space_update_ioeventfds().
@@ -360,12 +351,30 @@
virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
}
+ /*
+ * Set ->dataplane_started to false before draining so that host notifiers
+ * are not detached/attached anymore.
+ */
+ vblk->dataplane_started = false;
+
+ aio_context_acquire(s->ctx);
+
+ /* Wait for virtio_blk_dma_restart_bh() and in flight I/O to complete */
+ blk_drain(s->conf->conf.blk);
+
+ /*
+ * Try to switch bs back to the QEMU main loop. If other users keep the
+ * BlockBackend in the iothread, that's ok
+ */
+ blk_set_aio_context(s->conf->conf.blk, qemu_get_aio_context(), NULL);
+
+ aio_context_release(s->ctx);
+
qemu_bh_cancel(s->bh);
notify_guest_bh(s); /* final chance to notify guest */
/* Clean up guest notifier (irq) */
k->set_guest_notifiers(qbus->parent, nvqs, false);
- vblk->dataplane_started = false;
s->stopping = false;
}
