Am 13.02.2018 um 23:23 schrieb Michael S. Tsirkin:
> On Tue, Feb 13, 2018 at 09:53:58PM +0100, Peter Lieven wrote:
>> Am 21.12.2017 um 15:29 schrieb Michael S. Tsirkin:
>>> Backends don't need to know what frontend requested a reset,
>>> and notifying then from virtio_error is messy because
>>> virtio_error itself might be invoked from backend.
>>>
>>> Let's just set the status directly.
>>>
>>> Cc: qemu-sta...@nongnu.org
>>> Reported-by: Ilya Maximets <i.maxim...@samsung.com>
>>> Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
>>> ---
>>> hw/virtio/virtio.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
>>> index ad564b0..d6002ee 100644
>>> --- a/hw/virtio/virtio.c
>>> +++ b/hw/virtio/virtio.c
>>> @@ -2469,7 +2469,7 @@ void GCC_FMT_ATTR(2, 3) virtio_error(VirtIODevice
>>> *vdev, const char *fmt, ...)
>>> va_end(ap);
>>>
>>> if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
>>> - virtio_set_status(vdev, vdev->status |
>>> VIRTIO_CONFIG_S_NEEDS_RESET);
>>> + vdev->status = vdev->status | VIRTIO_CONFIG_S_NEEDS_RESET;
>>> virtio_notify_config(vdev);
>>> }
>>>
>>
>> Is it possible that this patch introduces a stall in I/O and a deadlock on a
>> drain all?
>>
>> I have seen Qemu VMs being I/O stalled and deadlocking on a vm stop command
>> in
>>
>> blk_drain_all. This happened after a longer storage outage.
>>
>>
>> I am asking just theoretically because I have seen this behaviour first when
>> we
>>
>> backported this patch in our stable 2.9 branch.
>>
>>
>> Thank you,
>>
>> Peter
> Well - this patch was introduced to fix a crash, but
> a well behaved VM should not trigger VIRTIO_CONFIG_S_NEEDS_RESET -
> did you see any error messages in the log when this triggered?
You mean in the guest or on the host? On the host I have seen nothing.
I actually did not know the reasoning behing this patch. I was just searching
for an explaination
for the strange I/O stalls that I have seen.
And it was not only one guest but a few hundreds. So I think I have to search
for another cause.
Thank you,
Peter
