Re: [Xen-devel] Broken PCI device passthrough, after XSA-302 fix?

[Jan Beulich <jbeulich@xxxxxxxx>]

On 04.01.2020 02:07, Marek Marczykowski-Górecki  wrote:
> I have a multi-function PCI device, behind a PCI bridge, that normally
> I assign to a single domain. But now it fails with:
> 
> (XEN) [VT-D]d14: 0000:04:00.0 owned by d0!<G><0>assign 0000:05:00.0 to dom14 
> failed (-22)

Is this on the 1st attempt, or after the device had already been
assigned to some (same or other) guest? After quite a bit of
staring at the code I can't seem to be able to spot a difference
in behavior for the 1st attempt, but you not saying explicitly
that it would only happen on subsequent ones makes me assume you
run into the issue right away.

> This is Xen 4.8.5 + XSA patches. It started happening after some update
> during last few months, not really sure which one.

Having a smaller window would of course help, as would ...

> I guess it is because quarantine feature, so initial ownership of
> 0000:05:00.0 is different than the bridge it is connected to.
> I'm not sure if relevant for this case, but I also set
> pcidev->rdm_policy = LIBXL_RDM_RESERVE_POLICY_RELAXED.
> 
> Booting with iommu=no-quarantine helps. Note I do not use `xl
> pci-assignable-add` command, only bind the device to the pciback driver
> in dom0.

... knowing whether behavior differs when using this preparatory
step.

Jan

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