perf/x86/intel: Fix Skylake FRONTEND MSR extrareg mask

Stephane pointed out that the extrareg mask was one bit too short.
The bubble width field was truncated by one bit. Fix that here.
Also add some extra comments on the reserved bits inside the event
select code.

Reported-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1441835640-21347-3-git-send-email-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index ef74c9d05f8227410e8bdb702004e1e67810f2ec..f63360be22387d4fb4cb30728f1834ee4cbd6228 100644 (file)
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -205,7 +205,11 @@ static struct extra_reg intel_skl_extra_regs[] __read_mostly = {
        INTEL_UEVENT_EXTRA_REG(0x01b7, MSR_OFFCORE_RSP_0, 0x3fffff8fffull, RSP_0),
        INTEL_UEVENT_EXTRA_REG(0x01bb, MSR_OFFCORE_RSP_1, 0x3fffff8fffull, RSP_1),
        INTEL_UEVENT_PEBS_LDLAT_EXTRA_REG(0x01cd),
-       INTEL_UEVENT_EXTRA_REG(0x01c6, MSR_PEBS_FRONTEND, 0x3fff17, FE),
+       /*
+        * Note the low 8 bits eventsel code is not a continuous field, containing
+        * some #GPing bits. These are masked out.
+        */
+       INTEL_UEVENT_EXTRA_REG(0x01c6, MSR_PEBS_FRONTEND, 0x7fff17, FE),
        EVENT_EXTRA_END
 };