From 8449bcf94986156a1476d6647c75ec1ce3db64d0 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Mon, 16 Jul 2018 09:37:32 +0100 Subject: [PATCH] virtio-scsi: fix hotplug ->reset() vs event race 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 Cc: Paolo Bonzini Cc: Fam Zheng Signed-off-by: Stefan Hajnoczi Message-Id: <20180716083732.3347-3-stefanha@redhat.com> Signed-off-by: Paolo Bonzini --- 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..5a3057d1f8 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) +{ + 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; } -- 2.11.4.GIT