Re: [PATCH] [RFC] virtio: Limit the retries on a virtio device reset

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Aug 24, 2017 at 07:07:42PM +0200, Pierre Morel wrote:
> > - we'll have to spread these tests all over the place.
> 
> I counted 19 places where to check if the reset went OK.
> 
> None of them touch the device anymore after reset and just free driver's
> resources.

... and then hypervisor uses the resources after free. Not good.

> So that if reset failed, nothing goes wrong, no device access, but the
> probability that the next probe fail is high. (If it ever succeed).
> 
> >    Allowing reset to fail would be better.
> 
> May be I did not understand what you mean.
> Testing the flag or a return value is as expensive.
> 
> Of course the implementation is a mater of taste.

If a function can fail it should return an error, not just set a flag.


> I notice two other things to do:
> 
> - May be adding a warning would be fine too.
> - Virtio_ccw may add a fail flag when allocation of CCW failed.
>   I did not find anything to do for virtio_mmio or legacy virtio_pci.
> 
> Regards,
> 
> Pierre