Re: Kernel panic in __pci_enable_msix_range on Xen PV with PCI passthrough

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

On Wed, Aug 25, 2021 at 05:55:09PM +0200, Jan Beulich wrote:
> On 25.08.2021 17:47, Marek Marczykowski-Górecki wrote:
> > If so, I guess the issue is the kernel trying to write directly, instead
> > of via some hypercall, right?
> 
> Indeed. Or to be precise - the kernel isn't supposed to be "writing" this
> at all. It is supposed to make hypercalls which may result in such writes.
> Such "mask everything" functionality imo is the job of the hypervisor
> anyway when talking about PV environments; HVM is a different thing here.

Ok, I dug a bit and found why it was working before: there is
pci_mask_ignore_mask variable, that is set to 1 for Xen PV (and only
then). This bypassed __pci_msi{x,}_desc_mask_irq(), but does not bypass the
new msix_mask_all().
Adding that check back fixes the issue - no crash, the device works,
although the driver doesn't seem to enable MSI/MSI-X (but that wasn't
the case before either).

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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