Commit 2a6e06b2 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

perf,x86: fix wrmsr_on_cpu() warning on suspend/resume

Commit 1d9d8639

 ("perf,x86: fix kernel crash with PEBS/BTS after
suspend/resume") fixed a crash when doing PEBS performance profiling
after resuming, but in using init_debug_store_on_cpu() to restore the
DS_AREA mtrr it also resulted in a new WARN_ON() triggering.

init_debug_store_on_cpu() uses "wrmsr_on_cpu()", which in turn uses CPU
cross-calls to do the MSR update.  Which is not really valid at the
early resume stage, and the warning is quite reasonable.  Now, it all
happens to _work_, for the simple reason that smp_call_function_single()
ends up just doing the call directly on the CPU when the CPU number
matches, but we really should just do the wrmsr() directly instead.

This duplicates the wrmsr() logic, but hopefully we can just remove the
wrmsr_on_cpu() version eventually.

Reported-and-tested-by: default avatarParag Warudkar <>
Signed-off-by: default avatarLinus Torvalds <>
parent 08637024
......@@ -732,8 +732,10 @@ void intel_ds_init(void)
void perf_restore_debug_store(void)
struct debug_store *ds = __this_cpu_read(cpu_hw_events.ds);
if (!x86_pmu.bts && !x86_pmu.pebs)
wrmsrl(MSR_IA32_DS_AREA, (unsigned long)ds);
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