Re: [PATCH v2] PCI: Mark broken INTx masking for Mellanox devices

[Gavin Shan <gwshan@linux.vnet.ibm.com>]

On Sun, Aug 03, 2014 at 08:57:39AM +0000, Eli Cohen wrote:
>>>
>>>What is the problem with masking the interrupts with the PCI command 
>>>register? I'm asking because I want to understand in which devices we 
>>>have the problem, and if it could be fixed by firmware guys.
>>>What are the implications of having the quirk?
>>>
>
>>The way to mask the interrupt through PCI command register isn't taking effect on IBM power platform. So we have to have the >quirk so that the interrupt could be masked from interrupt controller side with function disable_irq_nosync().
>>
>>If the interrupt can't be masked properly, we detect interrupt storm reported from host/guest when passing through those devices >via VFIO without suprise.
>
>Hi Gavin,
>Does it have any effect on performance. Also, can you tell in which cases interrupts need to be masked?
>

Eli, more code needed to be run for masking the LSI from interrupt controller
side than from PCI command register.

I was passing through Mellanox devices from host to guest with VFIO, and I
designated to use LSI in the guest side. More details could be found in
drivers/vfio/pci/vfio_pci_intrs.c::vfio_intx_handler()

Thanks,
Gavin