Re: [PATCH] MIPS: SB1250: Validate and update IRQ affinity

[Florian Fainelli]

Hi Maciej,

On 11/8/26 22:17, Maciej W. Rozycki wrote:
> On Fri, 6 Nov 2026, Maciej W. Rozycki wrote:
>
> > > sb1250_set_affinity() selects the first online CPU in the requested
> > > affinity mask without checking whether such a CPU exists. If the
> > > intersection is empty, the resulting CPU index is invalid and must
> > > not be passed to cpu_logical_map().
> > >
> > > Reject affinity masks containing no online CPU with -EINVAL before
> > > accessing the CPU mapping or interrupt mapper registers.
> >
> >   Why do you think this is needed?  The only case where an unvalidated mask
> > is passed is AFAICT with:
> >
> > /**
> >   * irq_force_affinity - Force the irq affinity of a given irq
> >   * @irq:	Interrupt to set affinity
> >   * @cpumask:	cpumask
> >   *
> >   * Same as irq_set_affinity, but without checking the mask against
> >   * online cpus.
> >   *
> >   * Solely for low level cpu hotplug code, where we need to make per
> >   * cpu interrupts affine before the cpu becomes online.
> >   */
> >
> > -- which does not apply here (nor for arch/mips/sibyte/bcm1480/irq.c,
> > which uses analogous code and should otherwise be updated accordingly)
> > since all the CPUs are onchip the SoC.
> >
> >   Have I missed anything?
> >
> > > Also update the effective affinity mask to reflect the single logical
> > > CPU selected as the interrupt target.
> >
> >   Likewise, why is it needed?  This code returns IRQ_SET_MASK_OK (should
> > really use the enumeration constant), so the caller will do the copy.
>
>   I can see it went to Linus already.  Can we please have it reverted?

Apologies for the late response, I was hoping Thomas would allow us to 
discuss this before applying. The effective-affinity update addresses 
this warning observed during boot:

genirq: irq_chip SB1250-IMR did not update eff. affinity mask of irq 2

IRQ_SET_MASK_OK causes irq_do_set_affinity() to copy the requested mask 
into irq_common_data.affinity, but it does not populate the separate 
effective_affinity mask when CONFIG_GENERIC_IRQ_EFFECTIVE_AFF_MASK is 
enabled. irq_validate_effective_affinity() then finds that mask empty 
and emits the warning.

Since the mapper selects a single CPU, 
irq_data_update_effective_affinity(d, cpumask_of(i)) records the actual 
target and addresses that warning. I should have included this in the 
commit message.

You are right about the empty-mask check, I will remove that part, 
revise the commit message accordingly, and use IRQ_SET_MASK_OK 
explicitly. BCM1480 should receive the analogous effective-affinity 
update as well.
--
Florian