[Qemu-devel] [PATCH 00/18] virtio-blk: Support "VIRTIO_CONFIG_S_NEEDS_RESET"

[Fam Zheng <famz@redhat.com>]

Currently, virtio code chooses to kill QEMU if the guest passes any invalid
data with vring. That has drawbacks such as losing unsaved data (e.g. when
guest user is writing a very long email), or possible denial of service in
a nested vm use case where virtio device is passed through.

virtio-1 has introduced a new status bit "NEEDS RESET" which could be used to
improve this by communicating the error state between virtio devices and
drivers. The device notifies guest upon setting the bit, then the guest driver
should detect this bit and report to userspace, or recover the device by
resetting it.

This series makes necessary changes in virtio core code, based on which
virtio-blk is converted. Other devices now keep the existing behavior by
passing in "error_abort". They will be converted in following series. The Linux
driver part will also be worked on.

One concern with this behavior change is that it's now harder to notice the
actual driver bug that caused the error, as the guest continues to run.  To
address that, we could probably add a new error action option to virtio
devices,  similar to the "read/write werror" in block layer, so the vm could be
paused and the management will get an event in QMP like pvpanic.  This work can
be done on top.



Fam Zheng (18):
  virtio: Return error from virtqueue_map_sg
  virtio: Return error from virtqueue_num_heads
  virtio: Return error from virtqueue_get_head
  virtio: Return error from virtqueue_next_desc
  virtio: Return error from virtqueue_get_avail_bytes
  virtio: Return error from virtqueue_pop
  virtio: Return error from virtqueue_avail_bytes
  virtio: Return error from virtio_add_queue
  virtio: Return error from virtio_del_queue
  virtio: Add macro for VIRTIO_CONFIG_S_NEEDS_RESET
  virtio: Add "needs_reset" flag to virtio device
  virtio: Return -EINVAL if the vdev needs reset in virtqueue_pop
  virtio-blk: Graceful error handling of virtqueue_pop
  qtest: Add "QTEST_FILTER" to filter test cases
  qtest: virtio-blk: Extract "setup" for future reuse
  libqos: Add qvirtio_needs_reset
  qtest: Add test case for "needs reset" of virtio-blk
  qtest: virtio-blk: Suppress virtio error messages in "make check"

 hw/9pfs/virtio-9p-device.c                     |   2 +-
 hw/9pfs/virtio-9p.c                            |   2 +-
 hw/block/dataplane/virtio-blk.c                |   9 +-
 hw/block/virtio-blk.c                          |  62 +++++--
 hw/char/virtio-serial-bus.c                    |  30 ++--
 hw/net/virtio-net.c                            |  36 +++--
 hw/scsi/virtio-scsi.c                          |   8 +-
 hw/virtio/virtio-balloon.c                     |  13 +-
 hw/virtio/virtio-rng.c                         |   6 +-
 hw/virtio/virtio.c                             | 214 ++++++++++++++++++-------
 include/hw/virtio/virtio-blk.h                 |   3 +-
 include/hw/virtio/virtio.h                     |  17 +-
 include/standard-headers/linux/virtio_config.h |   2 +
 tests/Makefile                                 |   6 +-
 tests/libqos/virtio.c                          |   5 +
 tests/libqos/virtio.h                          |   2 +
 tests/virtio-blk-test.c                        | 196 ++++++++++++++++++++--
 17 files changed, 482 insertions(+), 131 deletions(-)

-- 
1.9.3