Re: [PATCH 7/8] KVM: assigned dev: Introduce io_device for MSI-X MMIO accessing

Michael S. Tsirkin
2010-10-20T10:39:36Z

On Wed, Oct 20, 2010 at 11:46:47AM +0200, Avi Kivity wrote:
> >+ /* Only allow entry modification when entry was masked */
> >+ if (!entry_masked) {
> >+ printk(KERN_WARNING
> >+ "KVM: guest try to write unmasked MSI-X entry. "
> >+ "addr 0x%llx, len %d, val 0x%lx\n",
> >+ addr, len, new_val);
> >+ r = 0;
>
> What does the spec says about this situation?

That it's not allowed. However, existing userspace changes entries that
kvm thinks are unmasked, because it does not know how to tell kvm about
mask bits, so we need to keep supporting this.

--
MST