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perf/x86/amd/lbr: Discard erroneous branch entries 

[ Upstream commit 29297ffffb ]

The Revision Guide for AMD Family 19h Model 10-1Fh processors declares
Erratum 1452 which states that non-branch entries may erroneously be
recorded in the Last Branch Record (LBR) stack with the valid and
spec bits set.

Such entries can be recognized by inspecting bit 61 of the corresponding
LastBranchStackToIp register. This bit is currently reserved but if found
to be set, the associated branch entry should be discarded.

Signed-off-by: Sandipan Das <sandipan.das@amd.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://bugzilla.kernel.org/attachment.cgi?id=305518
Link: https://lore.kernel.org/r/3ad2aa305f7396d41a40e3f054f740d464b16b7f.1706526029.git.sandipan.das@amd.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Sandipan Das 2024-01-29 16:36:25 +05:30 committed by Greg Kroah-Hartman
parent 44479c7fef
commit 39da708cb2
1 changed files with 4 additions and 2 deletions
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6
arch/x86/events/amd/lbr.c
View File

@ -173,9 +173,11 @@ void amd_pmu_lbr_read(void)
/*
* Check if a branch has been logged; if valid = 0, spec = 0
* then no branch was recorded
* then no branch was recorded; if reserved = 1 then an
* erroneous branch was recorded (see Erratum 1452)
*/
if (!entry.to.split.valid && !entry.to.split.spec)
if ((!entry.to.split.valid && !entry.to.split.spec) ||
entry.to.split.reserved)
continue;
perf_clear_branch_entry_bitfields(br + out);