On Mon, 2022-09-05 at 15:49 +0800, Jason Wang wrote:

On Mon, Sep 5, 2022 at 3:15 PM Michael S. Tsirkin [off-list ref] wrote:

quoted

On Mon, Sep 05, 2022 at 12:53:41PM +0800, Jason Wang wrote:

quoted

Adding cond_resched() to the command waiting loop for a better
co-operation with the scheduler. This allows to give CPU a breath to
run other task(workqueue) instead of busy looping when preemption is
not allowed.

What's more important. This is a must for some vDPA parent to work
since control virtqueue is emulated via a workqueue for those parents.

Fixes: bda324fd037a ("vdpasim: control virtqueue support")

That's a weird commit to fix. so it fixes the simulator?

Yes, since the simulator is using a workqueue to handle control virtueue.

Uhmm... touching a driver for a simulator's sake looks a little weird. 

Additionally, if the bug is vdpasim, I think it's better to try to
solve it there, if possible.

Looking at vdpasim_net_work() and vdpasim_blk_work() it looks like
neither needs a process context, so perhaps you could rework it to run
the work_fn() directly from vdpasim_kick_vq(), at least for the control
virtqueue?

Thanks!

Paolo