From: Sandipan Das sandipan.das@amd.com
[ Upstream commit 29297ffffb0bf388778bd4b581a43cee6929ae65 ]
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.170652602... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/events/amd/lbr.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/events/amd/lbr.c b/arch/x86/events/amd/lbr.c index 38a75216c12cf..7b65bb890ba38 100644 --- a/arch/x86/events/amd/lbr.c +++ b/arch/x86/events/amd/lbr.c @@ -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);