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

[Oleksii Kurochko <oleksii.kurochko@gmail.com>]

On 1/12/26 6:05 PM, Jan Beulich wrote:
> On 12.01.2026 17:53, Oleksii Kurochko wrote:
>> On 1/7/26 4:47 PM, Jan Beulich wrote:
>>> On 24.12.2025 18:03, Oleksii Kurochko wrote:
>>>> @@ -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.
> I fear I don't follow: Why would the lowest value be picked, rather than the
> specified default (which would be 64 for RV64)? That's what I thought the
> default values are there (among other purposes).

But there is no default for RISC-V for config NR_CPUS:

   config NR_CPUS
	  int "Maximum number of CPUs"
	  range 1 1 if ARM && MPU
	  range 1 16383
	  default "256" if X86
	  default "1" if ARM && MPU
	  default "8" if ARM && RCAR3
	  default "4" if ARM && QEMU
	  default "4" if ARM && MPSOC
	  default "128" if ARM
	  help
	    ...

So a value from range [1, 16383] is chosen and based on the code of sym_validate_range():
         ...
	val = strtoll(sym->curr.val, NULL, base);
	val2 = sym_get_range_val(prop->expr->left.sym, base);
	if (val >= val2) {
		val2 = sym_get_range_val(prop->expr->right.sym, base);
		if (val <= val2)
			return;
	}
	if (sym->type == S_INT)
		sprintf(str, "%lld", val2);
	else
		sprintf(str, "0x%llx", val2);
         sym->curr.val = xstrdup(str);

First initialization of val2 it is the left value of the range [1, 16383],so it is 1
and val is 0 (I assume so that it is by initialization 0), thereby val2 = 1 will be
used as a value for NR_CPUS.

I also experimented by trying to update it to the range|2 16383|, and|CONFIG_NR_CPUS|
became 2.

~ Oleksii