qtest with multiple driver instances

qtest with multiple driver instances

[Christian Schoenebeck]

Hi,

I'm currently puzzled with what looks like a limitation of the qtest 
infrastructure: am I right that it's not possible to use multiple instances of 
the same driver with qtests?

Purpose: I need to add test cases for the 9p 'local' fs driver. So far we only 
have 9p qtests using the 'synth' fs driver. The problem is, both driver 
instances would pop up with the same QEMU driver name ("virtio-9p-pci"), and 
AFAICS qtests in general reference their driver instance by driver name only, 
which must be a) a unique driver name and b) must match the official QEMU 
driver name and c) all qtest driver instances are in a global space for all 
qtests.

Is there any workaround or something that I didn't see? Like letting qtests 
reference a driver instance by PCI address or something?

Right now the only option that I see is a hack: forcing one driver instance to 
use a different bus system like e.g. -> "virtio-9p-ccw" vs. "virtio-9p-pci".

Any hint appreciated!

Best regards,
Christian Schoenebeck

Re: qtest with multiple driver instances

[Thomas Huth]

On 24/09/2020 13.57, Christian Schoenebeck wrote:
> Hi,
> 
> I'm currently puzzled with what looks like a limitation of the qtest 
> infrastructure: am I right that it's not possible to use multiple instances of 
> the same driver with qtests?
> 
> Purpose: I need to add test cases for the 9p 'local' fs driver. So far we only 
> have 9p qtests using the 'synth' fs driver. The problem is, both driver 
> instances would pop up with the same QEMU driver name ("virtio-9p-pci"), and 
> AFAICS qtests in general reference their driver instance by driver name only, 
> which must be a) a unique driver name and b) must match the official QEMU 
> driver name and c) all qtest driver instances are in a global space for all 
> qtests.
> 
> Is there any workaround or something that I didn't see? Like letting qtests 
> reference a driver instance by PCI address or something?
> 
> Right now the only option that I see is a hack: forcing one driver instance to 
> use a different bus system like e.g. -> "virtio-9p-ccw" vs. "virtio-9p-pci".
> 
> Any hint appreciated!

I assume you are referring to the "qos" framework within the qtests? I
hope Laurent, Paolo or Emanuele can help with that question (now all on
CC:)...

 Thomas

Re: qtest with multiple driver instances

[Christian Schoenebeck]

On Donnerstag, 24. September 2020 15:50:43 CEST Thomas Huth wrote:
> On 24/09/2020 13.57, Christian Schoenebeck wrote:
> > Hi,
> > 
> > I'm currently puzzled with what looks like a limitation of the qtest
> > infrastructure: am I right that it's not possible to use multiple
> > instances of the same driver with qtests?
> > 
> > Purpose: I need to add test cases for the 9p 'local' fs driver. So far we
> > only have 9p qtests using the 'synth' fs driver. The problem is, both
> > driver instances would pop up with the same QEMU driver name
> > ("virtio-9p-pci"), and AFAICS qtests in general reference their driver
> > instance by driver name only, which must be a) a unique driver name and
> > b) must match the official QEMU driver name and c) all qtest driver
> > instances are in a global space for all qtests.
> > 
> > Is there any workaround or something that I didn't see? Like letting
> > qtests
> > reference a driver instance by PCI address or something?
> > 
> > Right now the only option that I see is a hack: forcing one driver
> > instance to use a different bus system like e.g. -> "virtio-9p-ccw" vs.
> > "virtio-9p-pci".
> > 
> > Any hint appreciated!
> 
> I assume you are referring to the "qos" framework within the qtests? I
> hope Laurent, Paolo or Emanuele can help with that question (now all on
> CC:)...
> 
>  Thomas

Yes, it looks like it is based on the qos subsystem underneath, i.e.:
tests/qtest/libqos/qgraph.h

Maybe I can use qos_node_contains() to make 2 "virtio-9p-pci" driver instances 
accessible for different qtests? It just seems there is no existing code doing 
that already, otherwise I could just copy & paste.

Best regards,
Christian Schoenebeck

Re: qtest with multiple driver instances

[Paolo Bonzini]

On 24/09/20 15:50, Thomas Huth wrote:
>> Is there any workaround or something that I didn't see? Like letting qtests 
>> reference a driver instance by PCI address or something?

The simplest way around this limitation is to move the -fsdev option
from the .before_cmd_line of the virtio-9p-*'s nodes to the .before
function of the test.  You can see an example in qtest/virtio-net-test.c.

It was done like this in virtio-9p simply because we only needed synth
fsdevs.

Paolo

Re: qtest with multiple driver instances

[Christian Schoenebeck]

On Donnerstag, 24. September 2020 16:27:53 CEST Paolo Bonzini wrote:
> On 24/09/20 15:50, Thomas Huth wrote:
> >> Is there any workaround or something that I didn't see? Like letting
> >> qtests
> >> reference a driver instance by PCI address or something?
> 
> The simplest way around this limitation is to move the -fsdev option
> from the .before_cmd_line of the virtio-9p-*'s nodes to the .before
> function of the test.  You can see an example in qtest/virtio-net-test.c.

Hmm, I keep that in mind. I first try though whether I can make a workaround 
by assigning a custom name to .edge_name (QOSGraphEdgeOptions) for each device 
instance. I have a feeling this might be simpler.

Thanks Paolo!

Best regards,
Christian Schoenebeck