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    SubjectRe: [PATCH v4 4/4] PCI: Limit pci_alloc_irq_vectors() to housekeeping CPUs
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    On Mon, Oct 26 2020 at 16:08, Jacob Keller wrote:
    > On 10/26/2020 3:49 PM, Thomas Gleixner wrote:
    >> On Mon, Oct 26 2020 at 18:22, Nitesh Narayan Lal wrote:
    >>> 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.
    >
    > Could this be handled with a callback to the driver/hw? I know Intel HW
    > should support this type of quiesce/shutdown.

    We can't have a callback from the interrupt shutdown code as you have to
    wait for the queue to drain packets in flight. Something like this

    mark queue as going down (no more tx queueing)
    tell hardware not to route RX packets to it
    consume pending RX
    wait for already queued TX packets to be sent

    Look what the block people did. They have a common multi-instance
    hotplug state and they register each context (queue) as an instance. The
    hotplug core invokes the corresponding callbacks when bringing a CPU up
    or when shutting it down.

    Thanks,

    tglx


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