Re: [PATCH vfio] vfio/pci: remove msi domain on msi disable

[Nelson, Shannon]

On 9/18/2023 4:32 PM, Jason Gunthorpe wrote:
> On Mon, Sep 18, 2023 at 10:48:54AM -0700, Nelson, Shannon wrote:
>
> > In our case, the VF device's msix count value found in PCI config space is
> > changed by device configuration management outside of the baremetal host and
> > read by the QEMU instance when it starts up, and then read by the vfio PCI
> > core when QEMU requests the first IRQ.
>
> Oh, you definitely can't do that!
>
> PCI config space is not allowed to change outside the OS's view and we
> added sriov_set_msix_vec_count() specifically as a way to provide the
> necessary synchronization between all the parts.
>
> Randomly changing, what should be immutable, parts of the config space
> from under a running OS is just non-compliant PCI behavior.

Hmmm... I guess I need to have a little chat with my friendly HW/FW folks.

Thanks,
sln