Re: [PATCH v4 4/4] PCI: Limit pci_alloc_irq_vectors() to housekeeping CPUs

[Jacob Keller]

On 10/26/2020 3:49 PM, Thomas Gleixner wrote:
> On Mon, Oct 26 2020 at 18:22, Nitesh Narayan Lal wrote:
>> On 10/26/20 5:50 PM, Thomas Gleixner wrote:
>>> But I still think that for curing that isolation stuff we want at least
>>> some information from the driver. Alternative solution would be to grant
>>> the allocation of interrupts and queues and have some sysfs knob to shut
>>> down queues at runtime. If that shutdown results in releasing the queue
>>> interrupt (via free_irq()) then the vector exhaustion problem goes away.
>>
>> I think this is close to what I and Marcelo were discussing earlier today
>> privately.
>>
>> I don't think there is currently a way to control the enablement/disablement of
>> interrupts from the userspace.
> 
> You cannot just disable the interrupt. You need to make sure that the
> associated queue is shutdown or quiesced _before_ the interrupt is shut
> down.
> 
> Thanks,
> 
>         tglx
> 

Could this be handled with a callback to the driver/hw? I know Intel HW
should support this type of quiesce/shutdown.

Thanks,
Jake