perf/x86/intel: Fix incorrect lbr_sel_mask value

This patch fixes a bug which was introduced by:

 b16a5b52eb90 ("perf/x86: Add option to disable reading branch flags/cycles")

In this patch, lbr_sel_mask is used to mask the lbr_select. But LBR_SEL_MASK
doesn't include the bit for LBR_CALL_STACK. So LBR call stack will never be
set in lbr_select.

This patch corrects the LBR_SEL_MASK by including all valid bits in
LBR_SELECT. Also, the LBR_CALL_STACK bit is different as other bit in
LBR_SELECT. It does not operate in suppress mode, so it needs to be
specially handled in intel_pmu_setup_hw_lbr_filter.

Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/1461231010-4399-1-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
index 6c3b7c1..1ca5d1e 100644 (file)
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -63,7 +63,7 @@ static enum {
 
 #define LBR_PLM (LBR_KERNEL | LBR_USER)
 
-#define LBR_SEL_MASK   0x1ff   /* valid bits in LBR_SELECT */
+#define LBR_SEL_MASK   0x3ff   /* valid bits in LBR_SELECT */
 #define LBR_NOT_SUPP   -1      /* LBR filter not supported */
 #define LBR_IGN                0       /* ignored */
 
@@ -610,8 +610,10 @@ static int intel_pmu_setup_hw_lbr_filter(struct perf_event *event)
         * The first 9 bits (LBR_SEL_MASK) in LBR_SELECT operate
         * in suppress mode. So LBR_SELECT should be set to
         * (~mask & LBR_SEL_MASK) | (mask & ~LBR_SEL_MASK)
+        * But the 10th bit LBR_CALL_STACK does not operate
+        * in suppress mode.
         */
-       reg->config = mask ^ x86_pmu.lbr_sel_mask;
+       reg->config = mask ^ (x86_pmu.lbr_sel_mask & ~LBR_CALL_STACK);
 
        if ((br_type & PERF_SAMPLE_BRANCH_NO_CYCLES) &&
            (br_type & PERF_SAMPLE_BRANCH_NO_FLAGS) &&