Re: [PATCH] x86/dpci: remove the dpci EOI timer

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Wed, Jan 13, 2021 at 04:31:33PM -0500, Jason Andryuk wrote:
> On Wed, Jan 13, 2021 at 1:34 PM Jason Andryuk <jandryuk@xxxxxxxxx> wrote:
> >
> > On Wed, Jan 13, 2021 at 1:06 PM Roger Pau Monné <roger.pau@xxxxxxxxxx> 
> > wrote:
> > >
> > > On Wed, Jan 13, 2021 at 10:48:52AM -0500, Jason Andryuk wrote:
> 
> <snip>
> 
> > > > I have some laptops running OpenXT where the USB controller and NIC
> > > > share an interrupt, and I assign them to different domains.  Qubes
> > > > would hit this as well.
> > >
> > > Is there any chance you could try the patch and see if you can hit the
> > > issue it was trying to fix?
> >
> > Would testing a backport to 4.12 be useful?  There were some file
> > renames, but it looks to apply.  The only difference is the 4.12
> > hvm_pirq_eoi hunk still has `(ent && ent->fields.mask) || `.  Maybe
> > backport commit eb298f32fac5ac "x86/dpci: EOI interrupt regardless of
> > its masking status" as well?

Yes, backporting that one should be harmless.

> Ok, I added these two patches to OpenXT with Xen 4.12.

Thanks!

> > Testing staging would take a little longer to make a machine available.
> >
> > I guess I'd also need to disable MSI for the two devices to ensure
> > they are both using the GSI?
> 
> lspci in dom0 shows the USB xhci controller, iwlwifi, and e1000e
> devices all with IRQ 16 and all with MSI disabled ("MSI: Enabled-").
> The two linux HVMs run with (PV) linux stubdoms, and the HVM kernels
> were started with pci=nosmi.  Networking through the iwlwifi device
> works for that VM while a mouse attached to the xhci controller is
> also working in the second VM.  Is there something else I should test?

Not really, I think that test should be good enough, the issue is that
we don't know which OS was seeing the issues noted by Kevin.

To make sure you trigger the right scenario, could you start the
iwlwifi HVM guest first, and then stress test the network device
(using iperf for example) while you bring up the second VM that uses
the xhci device?

Thanks, Roger.