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From b872baa52f5e8e8c84b3a19bb6cf5b6e92106fb9 Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Tue, 24 Jul 2018 15:13:08 +0200
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Subject: [PATCH 264/268] virtio-scsi: fix hotplug ->reset() vs event race
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RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
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Message-id: <20180724151308.20500-3-stefanha@redhat.com>
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Patchwork-id: 81486
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O-Subject: [RHEL-7.6 qemu-kvm-rhev PATCH 2/2] virtio-scsi: fix hotplug ->reset() vs event race
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Bugzilla: 1607891
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RH-Acked-by: Igor Mammedov <imammedo@redhat.com>
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RH-Acked-by: Pankaj Gupta <pagupta@redhat.com>
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RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
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There is a race condition during hotplug when iothread is used. It
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occurs because virtio-scsi may be processing command queues in the
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iothread while the monitor performs SCSI device hotplug.
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When a SCSI device is hotplugged the HotplugHandler->plug() callback is
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invoked and virtio-scsi emits a rescan event to the guest.
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If the guest submits a SCSI command at this point then it may be
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cancelled before hotplug completes. This happens because ->reset() is
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called by hw/core/qdev.c:device_set_realized() after
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HotplugHandler->plug() has been called and
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hw/scsi/scsi-disk.c:scsi_disk_reset() purges all requests.
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This patch uses the new HotplugHandler->post_plug() callback to emit the
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rescan event after ->reset(). This eliminates the race conditions where
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requests could be cancelled.
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Reported-by: l00284672 <lizhengui@huawei.com>
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Cc: Paolo Bonzini <pbonzini@redhat.com>
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Cc: Fam Zheng <famz@redhat.com>
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Message-Id: <20180716083732.3347-3-stefanha@redhat.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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(cherry picked from commit 8449bcf94986156a1476d6647c75ec1ce3db64d0)
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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hw/scsi/virtio-scsi.c | 11 ++++++++++-
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1 file changed, 10 insertions(+), 1 deletion(-)
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diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
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index 9f754c4..52a3c1d 100644
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--- a/hw/scsi/virtio-scsi.c
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+++ b/hw/scsi/virtio-scsi.c
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@@ -806,8 +806,16 @@ static void virtio_scsi_hotplug(HotplugHandler *hotplug_dev, DeviceState *dev,
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virtio_scsi_acquire(s);
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blk_set_aio_context(sd->conf.blk, s->ctx);
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virtio_scsi_release(s);
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-
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}
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+}
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+
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+/* Announce the new device after it has been plugged */
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+static void virtio_scsi_post_hotplug(HotplugHandler *hotplug_dev,
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+ DeviceState *dev)
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+{
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+ VirtIODevice *vdev = VIRTIO_DEVICE(hotplug_dev);
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+ VirtIOSCSI *s = VIRTIO_SCSI(vdev);
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+ SCSIDevice *sd = SCSI_DEVICE(dev);
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if (virtio_vdev_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG)) {
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virtio_scsi_acquire(s);
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@@ -977,6 +985,7 @@ static void virtio_scsi_class_init(ObjectClass *klass, void *data)
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vdc->start_ioeventfd = virtio_scsi_dataplane_start;
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vdc->stop_ioeventfd = virtio_scsi_dataplane_stop;
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hc->plug = virtio_scsi_hotplug;
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+ hc->post_plug = virtio_scsi_post_hotplug;
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hc->unplug = virtio_scsi_hotunplug;
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}
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--
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1.8.3.1
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