RE: [PATCH V2 7/8] vfio/pci: Support dynamic MSI-x

[Tian, Kevin]

> From: Alex Williamson <alex.williamson@xxxxxxxxxx>
> Sent: Tuesday, April 4, 2023 11:19 AM
> >
> > Thank you very much for your guidance. I will digest this some more and
> > see how wrappers could be used. In the mean time while trying to think
> how
> > to unify this code I do think there is an issue in this patch in that
> > the get_cached_msi_msg()/pci_write_msi_msg()
> > should not be in an else branch.
> >
> > Specifically, I think it needs to be:
> > 	if (msix) {
> > 		if (irq == -EINVAL) {
> > 			/* dynamically allocate interrupt */
> > 		}
> > 		get_cached_msi_msg(irq, &msg);
> > 		pci_write_msi_msg(irq, &msg);
> > 	}
> 
> Yes, that's looked wrong to me all along, I think that resolves it.
> Thanks,
> 

Do you mind elaborating why this change is required? I thought
pci_msix_alloc_irq_at() will compose a new msi message to write
hence no need to get cached value again in that case...