Re: [PATCH v2 4/4] KVM: Allow host IRQ sharing for passed-through PCI 2.3 devices

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Nov 02, 2010 at 08:30:25PM +0100, Jan Kiszka wrote:
> Am 02.11.2010 19:54, Michael S. Tsirkin wrote:
> > On Tue, Nov 02, 2010 at 07:51:39PM +0100, Jan Kiszka wrote:
> >> Am 02.11.2010 19:48, Jan Kiszka wrote:
> >>> Am 02.11.2010 19:40, Jan Kiszka wrote:
> >>>>>>>> @@ -199,6 +343,13 @@ static void kvm_free_assigned_device(struct kvm *kvm,
> >>>>>>>>  
> >>>>>>>>  	pci_reset_function(assigned_dev->dev);
> >>>>>>>>  
> >>>>>>>> +	/*
> >>>>>>>> +	 * Unmask the IRQ at PCI level once the reset is done - the next user
> >>>>>>>> +	 * may not expect the IRQ being masked.
> >>>>>>>> +	 */
> >>>>>>>> +	if (assigned_dev->pci_2_3)
> >>>>>>>> +		pci_2_3_irq_unmask(assigned_dev->dev);
> >>>>>>>> +
> >>>>>>>
> >>>>>>> Doesn't pci_reset_function clear mask bit? It seems to ...
> >>>>>>
> >>>>>> I was left with non-functional devices for the host here if I was not
> >>>>>> doing this. Need to recheck, but I think it was required.
> >>>>>
> >>>>> Interesting. Could you check why please?
> >>>>>
> >>>>
> >>>> Can't reproduce anymore. This was early code, maybe affected by some
> >>>> bits or buts that no longer exist.
> >>>>
> >>>> Spec says it's cleared on reset, so I removed those lines now.
> >>>>
> >>>
> >>> Hmpf, it just happened again: Guest was using my ath9k, I killed the
> >>> guest, lspci says DisINTx+. Strange. Is anyone (qemu) restoring the
> >>> config space after the reset, bringing the disable bit back?
> >>
> >> Or does the kernel cache the control word?
> >>
> >> Jan
> > 
> > Maybe it does, need to dig in drivers/pci. If it does this
> > might have other implications.
> 
> OK, that mystery is resolved now: pci_reset_function saves & restores
> the device state.
> 
> Jan

Aha. I wonder what other state we need to clear.

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