From: Stephane Eranian <eranian@xxxxxxxxxx> commit 6fc2e83077b05a061afe9b24f2fdff7a0434eb67 upstream. This patches fixes the LBR kernel crashes on Intel Atom and Intel Xeon. The kernel was assuming that if the CPU supports 64-bit format LBR, then it has an LBR_SELECT MSR. Atom, Xeon uses 64-bit LBR format but does not have LBR_SELECT. That was causing NULL pointer dereferences in a couple of places. Change-Id: Ia2a8290d9ad9553ea54fef81be7e9f8af4fbf9fa Signed-off-by: Stephane Eranian <eranian@xxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> Cc: Jiri Olsa <jolsa@xxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Vince Weaver <vincent.weaver@xxxxxxxxx> Cc: kan.liang@xxxxxxxxx Fixes: 96f3eda67fcf ("perf/x86/intel: Fix static checker warning in lbr enable") Link: http://lkml.kernel.org/r/1449182000-31524-2-git-send-email-eranian@xxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Signed-off-by: Denys Zagorui <dzagorui@xxxxxxxxx> --- arch/x86/kernel/cpu/perf_event_intel_lbr.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c index 8900400..2cdae69 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c +++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c @@ -153,7 +153,7 @@ static void __intel_pmu_lbr_enable(bool pmi) */ if (cpuc->lbr_sel) lbr_select = cpuc->lbr_sel->config; - if (!pmi) + if (!pmi && cpuc->lbr_sel) wrmsrl(MSR_LBR_SELECT, lbr_select); rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctl); @@ -432,8 +432,10 @@ static void intel_pmu_lbr_read_64(struct cpu_hw_events *cpuc) int out = 0; int num = x86_pmu.lbr_nr; - if (cpuc->lbr_sel->config & LBR_CALL_STACK) - num = tos; + if (cpuc->lbr_sel) { + if (cpuc->lbr_sel->config & LBR_CALL_STACK) + num = tos; + } for (i = 0; i < num; i++) { unsigned long lbr_idx = (tos - i) & mask; -- 2.10.3.dirty