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

[Thomas Gleixner]

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