Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.4 18/20] perf/x86: Fix LBR related crashes on Intel Atom | Date | Tue, 22 Aug 2017 12:10:01 -0700 |
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4.4-stable review patch. If anyone has any objections, please let me know.
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From: Stephane Eranian <eranian@google.com>
commit 6fc2e83077b05a061afe9b24f2fdff7a0434eb67 upstream.
This patches fixes the LBR kernel crashes on Intel Atom.
The kernel was assuming that if the CPU supports 64-bit format LBR, then it has an LBR_SELECT MSR. Atom uses 64-bit LBR format but does not have LBR_SELECT. That was causing NULL pointer dereferences in a couple of places.
Signed-off-by: Stephane Eranian <eranian@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: kan.liang@intel.com 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@google.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Denys Zagorui <dzagorui@cisco.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- arch/x86/kernel/cpu/perf_event_intel_lbr.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
--- 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 */ 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 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;
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