[Xen-devel] SRIOV VF reset problems

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

Hi,

I'm currently looking at a problem with a pass-through SR-IOV device where the 
guest driver triggers a VF reset via a back-door interface to the PF. The reset 
completes successfully but, in this scenario, it is up to the PF driver running 
in dom0 to restore the VF's config space. This is done by simply writing the 
bytes of config space saved prior to the reset (which may or may not be against 
the PCI spec) but causes a particular problem with MSI...

Because Xen has code to intercept writes to the capability, and vetoes any 
writes other than those which go to the MSI control register or the mask, the 
PF driver cannot restore the content MSI address register(s) after the reset. 
So, the question is how best to deal with this issue? For the moment I have a 
hack in place which calls pci_restore_msi_state() if an attempt is made to 
write the address which seems to work around the problem for me, but does not 
exactly seem like a proper solution. Thoughts anyone?

Cheers,

  Paul

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