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author | Kan Liang <kan.liang@linux.intel.com> | 2022-01-11 21:20:38 +0300 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-02-01 19:27:01 +0300 |
commit | b7bfc2c6cdd28fc250f5f8c3177293342bfe14a5 (patch) | |
tree | c59101c36dc1e70de9c02534d6f932f01c822672 /arch | |
parent | 1b4abcd997ade5cc0eac40cbb0c510015aa6fa0f (diff) | |
download | linux-b7bfc2c6cdd28fc250f5f8c3177293342bfe14a5.tar.xz |
perf/x86/intel: Add a quirk for the calculation of the number of counters on Alder Lake
commit 7fa981cad216e9f64f49e22112f610c0bfed91bc upstream.
For some Alder Lake machine with all E-cores disabled in a BIOS, the
below warning may be triggered.
[ 2.010766] hw perf events fixed 5 > max(4), clipping!
Current perf code relies on the CPUID leaf 0xA and leaf 7.EDX[15] to
calculate the number of the counters and follow the below assumption.
For a hybrid configuration, the leaf 7.EDX[15] (X86_FEATURE_HYBRID_CPU)
is set. The leaf 0xA only enumerate the common counters. Linux perf has
to manually add the extra GP counters and fixed counters for P-cores.
For a non-hybrid configuration, the X86_FEATURE_HYBRID_CPU should not
be set. The leaf 0xA enumerates all counters.
However, that's not the case when all E-cores are disabled in a BIOS.
Although there are only P-cores in the system, the leaf 7.EDX[15]
(X86_FEATURE_HYBRID_CPU) is still set. But the leaf 0xA is updated
to enumerate all counters of P-cores. The inconsistency triggers the
warning.
Several software ways were considered to handle the inconsistency.
- Drop the leaf 0xA and leaf 7.EDX[15] CPUID enumeration support.
Hardcode the number of counters. This solution may be a problem for
virtualization. A hypervisor cannot control the number of counters
in a Linux guest via changing the guest CPUID enumeration anymore.
- Find another CPUID bit that is also updated with E-cores disabled.
There may be a problem in the virtualization environment too. Because
a hypervisor may disable the feature/CPUID bit.
- The P-cores have a maximum of 8 GP counters and 4 fixed counters on
ADL. The maximum number can be used to detect the case.
This solution is implemented in this patch.
Fixes: ee72a94ea4a6 ("perf/x86/intel: Fix fixed counter check warning for some Alder Lake")
Reported-by: Damjan Marion (damarion) <damarion@cisco.com>
Reported-by: Chan Edison <edison_chan_gz@hotmail.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Damjan Marion (damarion) <damarion@cisco.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1641925238-149288-1-git-send-email-kan.liang@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
-rw-r--r-- | arch/x86/events/intel/core.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c index 03e6555aa8f1..dcf455525cfc 100644 --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -6187,6 +6187,19 @@ __init int intel_pmu_init(void) pmu->num_counters = x86_pmu.num_counters; pmu->num_counters_fixed = x86_pmu.num_counters_fixed; } + + /* + * Quirk: For some Alder Lake machine, when all E-cores are disabled in + * a BIOS, the leaf 0xA will enumerate all counters of P-cores. However, + * the X86_FEATURE_HYBRID_CPU is still set. The above codes will + * mistakenly add extra counters for P-cores. Correct the number of + * counters here. + */ + if ((pmu->num_counters > 8) || (pmu->num_counters_fixed > 4)) { + pmu->num_counters = x86_pmu.num_counters; + pmu->num_counters_fixed = x86_pmu.num_counters_fixed; + } + pmu->max_pebs_events = min_t(unsigned, MAX_PEBS_EVENTS, pmu->num_counters); pmu->unconstrained = (struct event_constraint) __EVENT_CONSTRAINT(0, (1ULL << pmu->num_counters) - 1, |