Re: [PATCH] vfio-pci: Fix MSI IRQ forwarding for without per-vector masking

[Leo Yan <leo.yan@linaro.org>]

Hi Jean-Philippe,

On Fri, Mar 22, 2019 at 01:29:24PM +0800, Leo Yan wrote:
> On Fri, Mar 22, 2019 at 01:23:08PM +0800, Leo Yan wrote:
> > If MSI doesn't support per-vector masking capability and
> > PCI_MSI_FLAGS_MASKBIT isn't set in message control field, the function
> > vfio_pci_msi_vector_write() will directly bail out for this case and
> > every vector's 'virt_state' keeps setting bit VFIO_PCI_MSI_STATE_MASKED.
> > 
> > This results in the state maintained in 'virt_state' cannot really
> > reflect the MSI hardware state; finally it will mislead the function
> > vfio_pci_update_msi_entry() to skip IRQ forwarding with below flow:
> > 
> > vfio_pci_update_msi_entry() {
> > 
> >   [...]
> > 
> >   if (msi_is_masked(entry->virt_state) == msi_is_masked(entry->phys_state))
> >       return 0;  ==> skip IRQ forwarding
> > 
> >   [...]
> > }
> > 
> > To fix this issue, when detect PCI_MSI_FLAGS_MASKBIT is not set in the
> > message control field, this patch simply clears bit
> > VFIO_PCI_MSI_STATE_MASKED for all vectors 'virt_state'; at the end
> > vfio_pci_update_msi_entry() can forward MSI IRQ successfully.
> 
> Just remind, this patch is for kvmtool but not for kernel.  Sorry I
> forget to add it in subject.

Gentle ping.  Not sure if this patch is reasonable, could you help to
give a review?

[...]

Thanks,
Leo Yan