5.15-stable review patch. If anyone has any objections, please let me know.
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From: Kan Liang kan.liang@linux.intel.com
commit 6f7f984fa85b305799076a1bcec941b9377587de upstream.
Starting from SPR, the basic uncore PMON information is retrieved from the discovery table (resides in an MMIO space populated by BIOS). It is called the discovery method. The existing value of the type->num_boxes is from the discovery table.
On some SPR variants, there is a firmware bug that makes the value from the discovery table incorrect. We use the value from the SPR_MSR_UNC_CBO_CONFIG MSR to replace the one from the discovery table:
38776cc45eb7 ("perf/x86/uncore: Correct the number of CHAs on SPR")
Unfortunately, the SPR_MSR_UNC_CBO_CONFIG isn't available for the EMR XCC (Always returns 0), but the above firmware bug doesn't impact the EMR XCC.
Don't let the value from the MSR replace the existing value from the discovery table.
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 Signed-off-by: Kan Liang kan.liang@linux.intel.com Signed-off-by: Ingo Molnar mingo@kernel.org Tested-by: Yunying Sun yunying.sun@intel.com Link: https://lore.kernel.org/r/20230905134248.496114-1-kan.liang@linux.intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/events/intel/uncore_snbep.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)
--- a/arch/x86/events/intel/uncore_snbep.c +++ b/arch/x86/events/intel/uncore_snbep.c @@ -6078,8 +6078,18 @@ void spr_uncore_cpu_init(void)
type = uncore_find_type_by_id(uncore_msr_uncores, UNCORE_SPR_CHA); if (type) { + /* + * The value from the discovery table (stored in the type->num_boxes + * of UNCORE_SPR_CHA) is incorrect on some SPR variants because of a + * firmware bug. Using the value from SPR_MSR_UNC_CBO_CONFIG to replace it. + */ rdmsrl(SPR_MSR_UNC_CBO_CONFIG, num_cbo); - type->num_boxes = num_cbo; + /* + * The MSR doesn't work on the EMR XCC, but the firmware bug doesn't impact + * the EMR XCC. Don't let the value from the MSR replace the existing value. + */ + if (num_cbo) + type->num_boxes = num_cbo; } spr_uncore_iio_free_running.num_boxes = uncore_type_max_boxes(uncore_msr_uncores, UNCORE_SPR_IIO); }