Re: [Qemu-block] [Qemu-devel] How to emulate block I/O timeout on qemu side?

[Dongli Zhang]

On 11/12/2018 03:13 PM, Marc Olson via Qemu-devel wrote:
> On 11/3/18 10:24 AM, Dongli Zhang wrote:
>> Hi all,
>>
>> I tried with the patch at:
>>
>> https://lists.gnu.org/archive/html/qemu-devel/2018-09/msg00394.html
>>
>> The patch is applied to qemu-3.0.0.
>>
>>
>> Below configuration is used to test the feature for guest VM nvme.
>>
>> # qemu-system-x86_64 \
>> -smp 4 -m 2000M -enable-kvm -vnc :0 -monitor stdio \
>> -net nic -net user,hostfwd=tcp::5022-:22 \
>> -drive file=virtio-disk.img,format=raw,if=none,id=disk0 \
>> -device virtio-blk-pci,drive=disk0,id=disk0-dev,num-queues=2,iothread=io1 \
>> -object iothread,id=io1 \
>> -device nvme,drive=nvme1,serial=deadbeaf1 \
>> -drive file=blkdebug:blkdebug.config:nvme.img,if=none,id=nvme1
>>
>> # cat blkdebug.config
>> [delay]
>> event = "write_aio"
>> latency = "9999999999"
>> sector = "40960"
>>
>>
>> The 'write' latency of sector=40960 is set to a very large value. When the 
>> I/O
>> is stalled in guest due to that sector=40960 is accessed, I do see below
>> messages in guest log:
>>
>> [   80.807755] nvme nvme0: I/O 11 QID 2 timeout, aborting
>> [   80.808095] nvme nvme0: Abort status: 0x4001
>>
>>
>> However, then nothing happens further. nvme I/O hangs in guest. I am not 
>> able to
>> kill the qemu process with Ctrl+C. Both vnc and qemu user net do not work. I
>> need to kill qemu with "kill -9"
>>
>>
>> The same result for virtio-scsi and qemu is stuck as well.
> While I didn't try virtio-scsi, I wasn't able to reproduce this behavior using
> nvme on Ubuntu 18.04 (4.15). What image and kernel version are you trying 
> against?

Would you like to reproduce the "aborting" message or the qemu hang?

guest image: ubuntu 16.04
guest kernel: mainline linux kernel (and default kernel in ubuntu 16.04)
qemu: qemu-3.0.0 (with the blkdebug delay patch)

Would you be able to see the nvme abort (which is indeed not supported by qemu)
message in guest kernel?

Once I see that message, I would not be able to kill the qemu-system-x86_64
command line with Ctrl+C.

Dongli Zhang