Re: [PATCH v9 13/31] x86,fs/resctrl: Handle events that can be read from any CPU

[Reinette Chatre <reinette.chatre@intel.com>]

Hi Tony,

On 8/29/25 12:33 PM, Tony Luck wrote:

> diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
> index 81c3fb6a95b6..7332e65b0e01 100644
> --- a/fs/resctrl/monitor.c
> +++ b/fs/resctrl/monitor.c
> @@ -356,15 +356,47 @@ static struct mbm_state *get_mbm_state(struct rdt_l3_mon_domain *d, u32 closid,
>  	return state ? &state[idx] : NULL;
>  }
>  
> +/*
> + * Called from preemptible context via a direct call of mon_event_count() for
> + * events that can be read on any CPU.
> + * Called from preemptible but non-migratable process context (mon_event_count()
> + * via smp_call_on_cpu()) OR non-preemptible context (mon_event_count() via
> + * smp_call_function_any()) for events that need to be read on a specific CPU.
> + */
> +static bool cpu_on_correct_domain(struct rmid_read *rr)
> +{
> +	struct cacheinfo *ci;
> +	int cpu;
> +
> +	/* Any CPU is OK for this event */
> +	if (rr->evt->any_cpu)
> +		return true;
> +
> +	cpu = smp_processor_id();
> +
> +	/* Single domain. Must be on a CPU in that domain. */
> +	if (rr->hdr)
> +		return cpumask_test_cpu(cpu, &rr->hdr->cpu_mask);
> +
> +	if (WARN_ON_ONCE(rr->r->rid != RDT_RESOURCE_L3))
> +		return false;
> +
> +	/* Summing domains that share a cache, must be on a CPU for that cache. */
> +	ci = get_cpu_cacheinfo_level(cpu, RESCTRL_L3_CACHE);

This patch itself looks good to me. I do expect this patch to look different after
the rebase since get_cpu_cacheinfo_level() is no longer called. I peeked at the new
version [1] and the series looks significantly different. The thing that I wanted to
check was if you kept the WARN_ON_ONCE(), which you did. Do you think it is still
necessary since there is no longer a get_cpu_cacheinfo_level() with a hardcoded L3
resource? Otherwise I assume that this check falls into the same category as the
earlier SNC related warnings and was not actually a check for the RESCTRL_L3_CACHE
that followed above?

Reinette

[1] https://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux.git/commit/?h=reinette-abmc-aet-wip&id=9f2f31b9dbb0d64c65b9aad754afdcb36935d719