Re: Random guest crashes since 5c34d002dcc7 ("virtio_pci: use shared interrupts for virtqueues")

[Michael S. Tsirkin]

On Fri, Mar 31, 2017 at 10:20:49AM +0200, Christoph Hellwig wrote:
> On Fri, Mar 31, 2017 at 06:22:31AM +0300, Michael S. Tsirkin wrote:
> > I'm not sure why does it fail after 32 on 64 bit, but as
> > virtio devices aren't limited to 32 vqs it looks like we
> > should go back to requesting the irq only once for all vqs.
> 
> Meh.
> 
> > 
> > Christoph, should I just revert for now, or do you
> > want to look into a smaller patch for this?
> 
> I think we'll need to do a different patch than just a simple revert,
> mostly because so much infrastructure depends on the patch.
> 
> I'll take a look over the weekend.
> 
> > Another question is looking into intx support - that
> > should work but it seems to be broken at the moment.
> 
> Does it?  I'm pretty sure I tested it back when I came up with the
> series by artifically disabling MSI-X in the kernel.  I can try this
> again, though.

I'm not 100% sure - what I see is that we do not handle failure to
request irqs correctly, we seem to fall back on intx but
the following freeze then blows up trying to free non-existing
vectors.

Does not seem to trigger with just msix off so maybe that is
simply failure to recover from an error correctly.


-- 
MST