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perf/x86: Fix LBR related crashes on Intel Atom 

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: 96f3eda67f ("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>
This commit is contained in:
Stephane Eranian 2015-12-03 23:33:17 +01:00 committed by Ingo Molnar
parent 61b87cae63
commit 6fc2e83077
1 changed files with 7 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
arch/x86/kernel/cpu/perf_event_intel_lbr.c
View File

@ -161,7 +161,7 @@ static void __intel_pmu_lbr_enable(bool pmi)
*/
if (cpuc->lbr_sel)
lbr_select = cpuc->lbr_sel->config & x86_pmu.lbr_sel_mask;
if (!pmi)
if (!pmi && cpuc->lbr_sel)
wrmsrl(MSR_LBR_SELECT, lbr_select);
rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
@ -430,7 +430,7 @@ static void intel_pmu_lbr_read_32(struct cpu_hw_events *cpuc)
*/
static void intel_pmu_lbr_read_64(struct cpu_hw_events *cpuc)
{
bool need_info = !(cpuc->lbr_sel->config & LBR_NO_INFO);
bool need_info = false;
unsigned long mask = x86_pmu.lbr_nr - 1;
int lbr_format = x86_pmu.intel_cap.lbr_format;
u64 tos = intel_pmu_lbr_tos();
@ -438,8 +438,11 @@ 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) {
need_info = !(cpuc->lbr_sel->config & LBR_NO_INFO);
if (cpuc->lbr_sel->config & LBR_CALL_STACK)
num = tos;
}
for (i = 0; i < num; i++) {
unsigned long lbr_idx = (tos - i) & mask;