Re: pci_msix_alloc_irq_at() affinity

[Shay Drori]

On 26/07/2024 16:48, Thomas Gleixner wrote:
> External email: Use caution opening links or attachments
>
>
> On Thu, Jul 25 2024 at 08:34, Shay Drori wrote:
> > I did some testing with pci_msix_alloc_irq_at() and I noticed that the
> > affinity provided, via “struct irq_affinity_desc *af_desc”, doesn’t have
> > any affect.
> >
> > After some digging, I found out that irq_setup_affinity(), which is
> > called by request_irq(), is setting the affinity as all the CPUs online,
> > ignoring the affinity provided in pci_msix_alloc_irq_at().
> > Is this on purpose or a bug?
>
> It's an oversight. So far this has only been used with managed
> interrupts and the non-managed parts at the beginning or end of the
> interrupt group have been assigned the default affinity which makes this
> obviously a non-problem because the startup code uses the default
> affinity too.
>
> > P.S. The bellow diff honors the affinity provided in
> > pci_msix_alloc_irq_at()
> >
> > --- a/kernel/irq/irqdesc.c
> > +++ b/kernel/irq/irqdesc.c
> > @@ -530,6 +530,7 @@ static int alloc_descs(unsigned int start, unsigned
> > int cnt, int node,
> >                                   flags = IRQD_AFFINITY_MANAGED |
> >                                           IRQD_MANAGED_SHUTDOWN;
> >                           }
> > +                 flags |= IRQD_AFFINITY_SET;
> >                           mask = &affinity->mask;
> >                           node = cpu_to_node(cpumask_first(mask));
> >                           affinity++;
>
> Looks about right, though the diff is whitespace damaged.
>
> Care to submit a proper patch?


sorry for the late reply, Yes.
on-top of which kernel branch to create the patch?


> Thanks,
>
>          tglx