Re: [Xen-devel] PCI Passthrough bug with x86 HVM

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

On Mon, Jun 24, 2019 at 11:47:09AM -0700, Stefano Stabellini wrote:
> + xen-devel
> 
> On Mon, 24 Jun 2019, Stefano Stabellini wrote:
> > Hi all,
> > 
> > I might have found a bug with PCI passthrough to a Linux HVM guest on
> > x86 with Xen 4.12. It is not easy for me to get access, and especially
> > change components, on this particular system, and I don't have access to
> > other x86 boxes at the moment, so apologies for the partial information
> > report. The setup is as follow:
> > 
> > - two PCI devices have been assigned to a HVM guest, everything is fine
> > - reboot the guest from inside, i.e. `reboot' in Linux
> > - after the reboot completes, only one device is assigned

Can you provide the xl debug log of the whole process?

> > Before the reboot, I see all the appropriate xenstore entries for both
> > devices. Everything is fine. After the reboot, I can only see the
> > xenstore entries of one device. It is as if the other device
> > "disappeared" without throwing any errors.

So there are no errors on the hypervisor dmesg or the xl logs at all?

> > Have you seen this before? Do you know if it has been fixed in staging?
> > I noticed this fix which seems to be very relevant:
> > 
> > https://lists.xenproject.org/archives/html/xen-devel/2018-11/msg01616.html
> > 
> > but it is already included in 4.12.

AFAICT your issue seems related to xl/libxl not properly re-adding the
devices on reboot. The fix above had to do with leaving devices in a
broken state under some circumstances (ie: they where always attached
to the guest, just not working properly).

Thanks, Roger.

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