Virtualization - Aug 2022 - Virtio-net - add timeouts to control commands

Hi Jason,
> Or reset but can we simply use interrupt instead of the busy waiting?
I agree that timeouts are not needed using interrupts.
This can be done, but seems like a big change.
All functions calling virtnet_send_command expect to get a response immediately.
This may be difficult, since some of the commands are sent in the
probe function.

On 8/24/22 11:16, Alvaro Karsz wrote:
> Hi Jason,
> 
>> Or reset but can we simply use interrupt instead of the busy waiting?
> 
> I agree that timeouts are not needed using interrupts.
Quite the contrary.
There is no guarantee that a completion for a given command will be 
signaled at all; if the completion is never posted to the virtio queue 
the VM will spin forever.
> This can be done, but seems like a big change.
> All functions calling virtnet_send_command expect to get a response
immediately.
> This may be difficult, since some of the commands are sent in the
> probe function.
This is a simplistic approach. _Any_ command sent via virtio will have 
to have some sort of handling in the host, so an immediate response is 
not guaranteed.
Especially virtio-block command will _not_ be handled immediately.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
hare at suse.de			                  +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 N?rnberg
HRB 36809 (AG N?rnberg), GF: Felix Imend?rffer

On Wed, Aug 24, 2022 at 5:16 PM Alvaro Karsz <alvaro.karsz at
solid-run.com> wrote:
>
> Hi Jason,
>
> > Or reset but can we simply use interrupt instead of the busy waiting?
>
> I agree that timeouts are not needed using interrupts.
> This can be done, but seems like a big change.
> All functions calling virtnet_send_command expect to get a response
immediately.
> This may be difficult, since some of the commands are sent in the
> probe function.
We can put the process into interruptible sleep, then it should be fine?

(FYI, some transport specific methods may sleep e.g ccw).

Thanks
>