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[Qemu-devel] [PATCH 2/2] virtio-scsi: fix hotplug ->reset() vs event rac
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PATCH 2/2] virtio-scsi: fix hotplug ->reset() vs event race |
Date: |
Tue, 10 Jul 2018 16:50:37 +0100 |
There is a race condition during hotplug when iothread is used. It
occurs because virtio-scsi may be processing command queues in the
iothread while the monitor performs SCSI device hotplug.
When a SCSI device is hotplugged the HotplugHandler->plug() callback is
invoked and virtio-scsi emits a rescan event to the guest.
If the guest submits a SCSI command at this point then it may be
cancelled before hotplug completes. This happens because ->reset() is
called by hw/core/qdev.c:device_set_realized() after
HotplugHandler->plug() has been called and
hw/scsi/scsi-disk.c:scsi_disk_reset() purges all requests.
This patch uses the new HotplugHandler->post_plug() callback to emit the
rescan event after ->reset(). This eliminates the race conditions where
requests could be cancelled.
Reported-by: l00284672 <address@hidden>
Cc: Paolo Bonzini <address@hidden>
Cc: Fam Zheng <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
hw/scsi/virtio-scsi.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index 3aa99717e2..1ec808e6fd 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -797,8 +797,16 @@ static void virtio_scsi_hotplug(HotplugHandler
*hotplug_dev, DeviceState *dev,
virtio_scsi_acquire(s);
blk_set_aio_context(sd->conf.blk, s->ctx);
virtio_scsi_release(s);
-
}
+}
+
+/* Announce the new device after it has been plugged */
+static void virtio_scsi_post_hotplug(HotplugHandler *hotplug_dev,
+ DeviceState *dev, Error **errp)
+{
+ VirtIODevice *vdev = VIRTIO_DEVICE(hotplug_dev);
+ VirtIOSCSI *s = VIRTIO_SCSI(vdev);
+ SCSIDevice *sd = SCSI_DEVICE(dev);
if (virtio_vdev_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG)) {
virtio_scsi_acquire(s);
@@ -968,6 +976,7 @@ static void virtio_scsi_class_init(ObjectClass *klass, void
*data)
vdc->start_ioeventfd = virtio_scsi_dataplane_start;
vdc->stop_ioeventfd = virtio_scsi_dataplane_stop;
hc->plug = virtio_scsi_hotplug;
+ hc->post_plug = virtio_scsi_post_hotplug;
hc->unplug = virtio_scsi_hotunplug;
}
--
2.17.1
[Qemu-devel] [PATCH 2/2] virtio-scsi: fix hotplug ->reset() vs event race,
Stefan Hajnoczi <=
Re: [Qemu-devel] [PATCH 0/2] virtio-scsi: fix hotplug ->reset() vs event race, Fam Zheng, 2018/07/10
Re: [Qemu-devel] [PATCH 0/2] virtio-scsi: fix hotplug ->reset() vs event race, l00284672, 2018/07/10