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

[Maciej W. Rozycki]

On Tue, 3 Nov 2026, Florian Fainelli 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.

  Maciej