blockdev: reset werror/rerror on drive_del

Paolo Bonzini <pbonzini@redhat.com> suggested the following test case:

1. Launch a guest and wait at the GRUB boot menu:

  qemu-system-x86_64 -enable-kvm -m 1024 \
   -drive if=none,cache=none,file=test.img,id=foo,werror=stop,rerror=stop
   -device virtio-blk-pci,drive=foo,id=virtio0,addr=4

2. Hot unplug the device:

  (qemu) drive_del foo

3. Select the first boot menu entry

Without this patch the guest pauses due to ENOMEDIUM.  The guest is
stuck in a continuous pause loop since the I/O request is retried and
fails immediately again when the guest is resumed.

With this patch the error is reported to the guest.

Note that this scenario actually happens sometimes during libvirt disk
hot unplug, where device_del is followed by drive_del.  I/O may still be
submitted to the drive after drive_del if the guest does not process the
PCI hot unplug notification.

Reported-by: Dafna Ron <dron@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 293c51a6ee369228633a8428ab689f14c045ff98)

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/blockdev.c b/blockdev.c
index 7c9d8dd0acfe7f136f4601cebad92157cee7d5ae..625d04123de1298eafd0498c56043efe52f6d3cc 100644 (file)
--- a/blockdev.c
+++ b/blockdev.c
@@ -1108,6 +1108,10 @@ int do_drive_del(Monitor *mon, const QDict *qdict, QObject **ret_data)
      */
     if (bdrv_get_attached_dev(bs)) {
         bdrv_make_anon(bs);
+
+        /* Further I/O must not pause the guest */
+        bdrv_set_on_error(bs, BLOCKDEV_ON_ERROR_REPORT,
+                          BLOCKDEV_ON_ERROR_REPORT);
     } else {
         drive_uninit(drive_get_by_blockdev(bs));
     }

diff --git a/hmp-commands.hx b/hmp-commands.hx
index 9cea4151b9cdb929e4235a255948ff61698c965b..4f5a3fd7d56a48dbd44e3d4b43d62a8127ca3432 100644 (file)
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -185,6 +185,8 @@ Remove host block device.  The result is that guest generated IO is no longer
 submitted against the host device underlying the disk.  Once a drive has
 been deleted, the QEMU Block layer returns -EIO which results in IO
 errors in the guest for applications that are reading/writing to the device.
+These errors are always reported to the guest, regardless of the drive's error
+actions (drive options rerror, werror).
 ETEXI
 
     {