Re: [PATCH 3/4] nvme: pci: pass IRQF_RESCURE_THREAD to request_threaded_irq

From: Ming Lei
Date: Tue Aug 27 2019 - 21:45:42 EST

On Tue, Aug 27, 2019 at 08:10:42AM -0700, Bart Van Assche wrote:
> On 8/27/19 1:53 AM, Ming Lei wrote:
> > If one vector is spread on several CPUs, usually the interrupt is only
> > handled on one of these CPUs.
> Is that perhaps a limitation of x86 interrupt handling hardware? See also
> the description of physical and logical destination mode of the local APIC
> in the Intel documentation.
> Does that limitation also apply to other platforms than x86?

Please see the following excellent explanation from Thomas.

Especially the following words:

So at some point we ripped out the multi target support on X86 and moved
everything to single target delivery mode.

Other architectures never supported multi target delivery either due to
hardware restrictions or for similar reasons why X86 dropped it. There
might be a few architectures which support it, but I have no overview at
the moment.