Re: [Qemu-devel] [PATCH 18/38] ivshmem: Leave INTx alone when using MSI-X

[Paolo Bonzini]

On 01/03/2016 18:14, Marc-André Lureau wrote:
> > +    /*
> > +     * Note: we don't use INTx with IVSHMEM_MSI at all, so this is a
> > +     * bald-faced lie then.  But it's a backwards compatible lie.
> > +     */
> >      pci_config_set_interrupt_pin(pci_conf, 1);
> 
> I am not sure how much of a problem this is. Apparently, other devices
> claim interrupt and msi (ich, hda, pvscsi)
> 
> Better ask someone more familiar with PCI details.

The interrupt pin is read-only and just helps the OS figure out which
interrupt is routed to intx.  If you return early from
ivshmem_update_irq if IVSHMEM_MSI, you should skip this line too.

I think it's better to leave this line in and check

    if (msix_enabled(pci_dev)) {
        return;
    }

in ivshmem_update_irq instead.  This matches what xhci does, for example.

Paolo