Re: [Xen-devel] Xen-unstable: pci-passthrough regression bisected to: x86/smp: use APIC ALLBUT destination shorthand when possible

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

On Mon, Feb 03, 2020 at 01:30:55PM +0100, Sander Eikelenboom wrote:
> On 03/02/2020 13:23, Roger Pau Monné wrote:
> > On Mon, Feb 03, 2020 at 09:33:51AM +0100, Sander Eikelenboom wrote:
> >> Hi Roger,
> >>
> >> Last week I encountered an issue with the PCI-passthrough of a USB 
> >> controller. 
> >> In the guest I get:
> >>     [ 1143.313756] xhci_hcd 0000:00:05.0: xHCI host not responding to stop 
> >> endpoint command.
> >>     [ 1143.334825] xhci_hcd 0000:00:05.0: xHCI host controller not 
> >> responding, assume dead
> >>     [ 1143.347364] xhci_hcd 0000:00:05.0: HC died; cleaning up
> >>     [ 1143.356407] usb 1-2: USB disconnect, device number 2
> >>
> >> Bisection turned up as the culprit: 
> >>    commit 5500d265a2a8fa63d60c08beb549de8ec82ff7a5
> >>    x86/smp: use APIC ALLBUT destination shorthand when possible
> > 
> > Sorry to hear that, let see if we can figure out what's wrong.
> 
> No problem, that is why I test stuff :)
> 
> >> I verified by reverting that commit and now it works fine again.
> > 
> > Does the same controller work fine when used in dom0?
> 
> Will test that, but as all other pci devices in dom0 work fine,
> I assume this controller would also work fine in dom0 (as it has also
> worked fine for ages with PCI-passthrough to that guest and still works
> fine when reverting the referenced commit).

Is this the only device that fails to work when doing pci-passthrough,
or other devices also don't work with the mentioned change applied?

Have you tested on other boxes?

> I don't know if your change can somehow have a side effect
> on latency around the processing of pci-passthrough ?

Hm, the mentioned commit should speed up broadcast IPIs, but I don't
see how it could slow down other interrupts. Also I would think the
domain is not receiving interrupts from the device, rather than
interrupts being slow.

Can you also paste the output of lspci -v for that xHCI device from
dom0?

Thanks, Roger.

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