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OpenCloudOS-Kernel/arch/x86/events
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Stephane Eranian 11745ecfe8 perf/x86/intel/uncore: Fix broken read_counter() for SNB IMC PMU 
Existing code was generating bogus counts for the SNB IMC bandwidth counters:

$ perf stat -a -I 1000 -e uncore_imc/data_reads/,uncore_imc/data_writes/
     1.000327813           1,024.03 MiB  uncore_imc/data_reads/
     1.000327813              20.73 MiB  uncore_imc/data_writes/
     2.000580153         261,120.00 MiB  uncore_imc/data_reads/
     2.000580153              23.28 MiB  uncore_imc/data_writes/

The problem was introduced by commit:
  07ce734dd8 ("perf/x86/intel/uncore: Clean up client IMC")

Where the read_counter callback was replace to point to the generic
uncore_mmio_read_counter() function.

The SNB IMC counters are freerunnig 32-bit counters laid out contiguously in
MMIO. But uncore_mmio_read_counter() is using a readq() call to read from
MMIO therefore reading 64-bit from MMIO. Although this is okay for the
uncore_perf_event_update() function because it is shifting the value based
on the actual counter width to compute a delta, it is not okay for the
uncore_pmu_event_start() which is simply reading the counter  and therefore
priming the event->prev_count with a bogus value which is responsible for
causing bogus deltas in the perf stat command above.

The fix is to reintroduce the custom callback for read_counter for the SNB
IMC PMU and use readl() instead of readq(). With the change the output of
perf stat is back to normal:
$ perf stat -a -I 1000 -e uncore_imc/data_reads/,uncore_imc/data_writes/
     1.000120987             296.94 MiB  uncore_imc/data_reads/
     1.000120987             138.42 MiB  uncore_imc/data_writes/
     2.000403144             175.91 MiB  uncore_imc/data_reads/
     2.000403144              68.50 MiB  uncore_imc/data_writes/

Fixes: 07ce734dd8 ("perf/x86/intel/uncore: Clean up client IMC")
Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Link: https://lore.kernel.org/r/20220803160031.1379788-1-eranian@google.com
 		2022-08-27 00:05:38 +02:00
..
amd perf/x86/amd/uncore: Add PerfMonV2 RDPMC assignments 2022-06-13 10:15:14 +02:00
intel perf/x86/intel/uncore: Fix broken read_counter() for SNB IMC PMU 2022-08-27 00:05:38 +02:00
zhaoxin x86: Fix various typos in comments 2021-03-18 15:31:53 +01:00
Kconfig perf/x86/Kconfig: Fix indentation in the Kconfig file 2022-05-25 15:54:26 +02:00
Makefile perf/x86/rapl: Fix RAPL config variable bug 2020-06-02 11:52:56 +02:00
core.c x86: events: Do not return bogus capabilities if PMU is broken 2022-06-08 13:06:15 -04:00
msr.c perf/x86/msr: Add new Alder Lake and Raptor Lake support 2022-05-11 16:27:08 +02:00
perf_event.h ARM: 2022-08-04 14:59:54 -07:00
probe.c perf/x86/rapl: Add msr mask support 2021-02-10 14:44:54 +01:00
probe.h perf/x86/rapl: Add msr mask support 2021-02-10 14:44:54 +01:00
rapl.c perf/x86/rapl: fix AMD event handling 2022-01-18 12:09:48 +01:00