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

[Jan Kiszka <jan.kiszka@web.de>]

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Am 02.11.2010 20:53, Michael S. Tsirkin wrote:
> 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.
> 

Maybe just save/restore before/after assigning the device?

Jan


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