Re: [PATCH v1 05/15] xen/riscv: implement stub for smp_send_event_check_mask()

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

On 1/7/26 4:47 PM, Jan Beulich wrote:
> On 24.12.2025 18:03, Oleksii Kurochko wrote:
> > --- a/xen/arch/riscv/smp.c
> > +++ b/xen/arch/riscv/smp.c
> > @@ -1,3 +1,4 @@
> > +#include <xen/cpumask.h>
> >   #include <xen/smp.h>
> >   
> >   /*
> > @@ -13,3 +14,10 @@
> >   struct pcpu_info pcpu_info[NR_CPUS] = { [0 ... NR_CPUS - 1] = {
> >       .processor_id = NR_CPUS,
> >   }};
> > +
> > +void smp_send_event_check_mask(const cpumask_t *mask)
> > +{
> > +#if CONFIG_NR_CPUS > 1
> > +# error "smp_send_event_check_mask() unimplemented"
> > +#endif
> > +}
> CONFIG_NR_CPUS is 64 by default for 64-bit arch-es, from all I can tell, also
> for RISC-V. And there's no "override" in riscv64_defconfig. How is the above
> going to work in CI? Then again I must be overlooking something, as the config
> used in CI has CONFIG_NR_CPUS=1. Just that I can't tell why that is.
It is 1 because of the defintion of NR_CPUS in KConfig:
config NR_CPUS
        int "Maximum number of CPUs"
        range 1 1 if ARM && MPU
        range 1 16383
        .... ( all other range props are condtional and there is no RISC-V in 
dependency)
so for RISC-V "range 1 16383" used and CONFIG_NR_CPUS is set to the minimal of 
this range,
so it is 1.

> And no, I'm not meaning to ask that you override NR_CPUS (and wherever such an
> override would live, I think it would better be dropped rather sooner than
> later). Instead an option may be this:
>
> void smp_send_event_check_mask(const cpumask_t *mask)
> {
> #if CONFIG_NR_CPUS > 1
>      BUG_ON(!cpumask_subset(mask, cpumask_of(0)));
> #endif
> }
>
> (I can't tell off the top of my head whether an empty mask may be passed to this
> function. If not, cpumask_equal() could be used as well.)
I will double-check. Thanks for such hint.

> Of course the #if may then not be necessary at all, and a TODO comment may want
> putting there instead.
With suggested above approach, I think it isn't really needed to use #if.

Thanks!

~ Oleksii