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

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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.

> -- 
> Siemens AG, Corporate Technology, CT T DE IT 1
> Corporate Competence Center Embedded Linux
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