Re: [kvm-unit-tests PATCH 6/7] s390x: virtio tests setup

[Thomas Huth <thuth@redhat.com>]

On 08/11/2021 14.00, Pierre Morel wrote:
> 
> 
> On 11/3/21 09:14, Thomas Huth wrote:
>> On 03/11/2021 08.56, Andrew Jones wrote:
>>> On Fri, Aug 27, 2021 at 12:17:19PM +0200, Pierre Morel wrote:
>>>> +
>>>> +#define VIRTIO_ID_PONG         30 /* virtio pong */
>>>
>>> I take it this is a virtio test device that ping-pong's I/O. It sounds
>>> useful for other VIRTIO transports too. Can it be ported? Hmm, I can't
>>> find it in QEMU at all?
>>
>> I also wonder whether we could do testing with an existing device instead? 
>> E.g. do a loopback with a virtio-serial device? Or use two virtio-net 
>> devices, connect them to a QEMU hub and send a packet from one device to 
>> the other? ... that would be a little bit more complicated here, but would 
>> not require a PONG device upstream first, so it could also be used for 
>> testing older versions of QEMU...
>>
>>   Thomas
>>
>>
> 
> Yes having a dedicated device has the drawback that we need it in QEMU.
> On the other hand using a specific device, serial or network, wouldn't we 
> get trapped with a reduce set of test possibilities?
> 
> The idea was to have a dedicated test device, which could be flexible and 
> extended to test all VIRTIO features, even the current implementation is yet 
> far from it.

Do you have anything in the works that could only be tested with a dedicated 
test device? If not, I'd rather go with the loopback via virtio-net, I think 
(you can peek into the s390-ccw bios sources to see how to send packets via 
virtio-net, shouldn't be too hard to do, I think).

The pong device could later be added on top for additional tests that are 
not possible with virtio-net. And having some basic tests with virito-net 
has also the advantage that the k-u-t work with QEMU binaries where the pong 
device is not available, e.g. older versions and downstream versions that 
only enable the bare minimum of devices to keep the attack surface small.

  Thomas