Messages in this thread | | | Date | Sun, 3 Sep 2023 10:40:58 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] perf/x86/uncore: Correct the number of CHAs on EMR |
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* kan.liang@linux.intel.com <kan.liang@linux.intel.com> wrote:
> From: Kan Liang <kan.liang@linux.intel.com> > > The MSR UNC_CBO_CONFIG, which was used to detect the number of CHAs on > SPR, is broken on EMR XCC. It always returns 0. > > Roll back to the discovery method, which can give the correct number for > this case. > > Fixes: 38776cc45eb7 ("perf/x86/uncore: Correct the number of CHAs on SPR") > Reported-by: Stephane Eranian <eranian@google.com> > Reported-by: Yunying Sun <yunying.sun@intel.com> > Tested-by: Yunying Sun <yunying.sun@intel.com> > Signed-off-by: Kan Liang <kan.liang@linux.intel.com> > --- > arch/x86/events/intel/uncore_snbep.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/events/intel/uncore_snbep.c b/arch/x86/events/intel/uncore_snbep.c > index d49e90dc04a4..c41d7d46481c 100644 > --- a/arch/x86/events/intel/uncore_snbep.c > +++ b/arch/x86/events/intel/uncore_snbep.c > @@ -6475,7 +6475,9 @@ void spr_uncore_cpu_init(void) > type = uncore_find_type_by_id(uncore_msr_uncores, UNCORE_SPR_CHA); > if (type) { > rdmsrl(SPR_MSR_UNC_CBO_CONFIG, num_cbo); > - type->num_boxes = num_cbo; > + /* The MSR doesn't work on the EMR XCC. Roll back to the discovery method. */ > + if (num_cbo) > + type->num_boxes = num_cbo;
So in the zero case we don't write type->num_boxes and leave it as-is.
How does this fall back to the discovery method, is the existing (default?) value of type->num_boxes some special value?
Thanks,
Ingo
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