Hi James,
On Wed, Aug 27, 2025 at 06:11:43PM +0100, James Morse wrote:
> Hi Dave,
>
> On 27/08/2025 11:46, Dave Martin wrote:
> > Hi,
> >
> > On Fri, Aug 22, 2025 at 03:29:43PM +0000, James Morse wrote:
> >> MPAM needs to know the size of a cache associated with a particular CPU.
> >> The DT/ACPI agnostic way of doing this is to ask cacheinfo.
> >>
> >> Add a helper to do this.
>
> >> diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
> >> index 2dcbb69139e9..e12d6f2c6a57 100644
> >> --- a/include/linux/cacheinfo.h
> >> +++ b/include/linux/cacheinfo.h
> >> @@ -148,6 +148,21 @@ static inline int get_cpu_cacheinfo_id(int cpu, int level)
> >> return ci ? ci->id : -1;
> >> }
> >>
> >> +/**
> >> + * get_cpu_cacheinfo_size() - Get the size of the cache.
> >> + * @cpu: The cpu that is associated with the cache.
> >> + * @level: The level of the cache as seen by @cpu.
> >> + *
> >> + * Callers must hold the cpuhp lock.
> >> + * Returns the cache-size on success, or 0 for an error.
> >> + */
> >
> > Nit: Maybe use the wording
> >
> > cpuhp lock must be held.
> >
> > in the kerneldoc here, to match the other helpers it sits alongside.
> >
> > Otherwise, looks reasonable.
>
> Sure,
>
>
> >> +static inline unsigned int get_cpu_cacheinfo_size(int cpu, int level)
> >> +{
> >> + struct cacheinfo *ci = get_cpu_cacheinfo_level(cpu, level);
> >> +
> >> + return ci ? ci->size : 0;
> >> +}
> >> +
> >
> > Orphaned function?
> >
> > Can fs/resctrl/rdtgroup.c:rdtgroup_cbm_to_size() be ported to use this?
> > If so, this wouldn't just be dead code in this series.
>
> Ah - I thought the MPAM driver was pulling this value in, but its the resctrl glue code.
> I was trying to reduce the number of trees this touches - its probably best to kick this
> into the next series that adds the resctrl code as its pretty trivial.
>
>
> Thanks,
>
> James
Sure, that also works.
Cheers
---Dave
