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

On Thu, Aug 24, 2017 at 07:07:42PM +0200, Pierre Morel wrote:

quoted

- 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).

quoted

   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