Messages in this thread | | | Subject | Re: [V2 PATCH 0/6] x86, NMI: give NMI handler a face-lift | From | Peter Zijlstra <> | Date | Sat, 20 Nov 2010 00:09:39 +0100 |
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On Fri, 2010-11-19 at 17:59 -0500, Don Zickus wrote: > +++ b/arch/x86/kernel/cpu/perf_event.c > @@ -381,6 +381,19 @@ static void release_pmc_hardware(void) {} > > #endif > > +static bool check_hw_exists(void) > +{ > + u64 val, val_new; > + > + val = 0xabcdUL; > + (void) checking_wrmsrl(x86_pmu.perfctr, val); > + rdmsrl(x86_pmu.perfctr, val_new);
Yeah, this looks about right, although for extreme prudence I'd also use a checking_rdmsrl().
> + if (val != val_new) > + return false; > + > + return true; > +} > + > static void reserve_ds_buffers(void); > static void release_ds_buffers(void); > > @@ -1371,6 +1385,12 @@ void __init init_hw_perf_events(void) > > pmu_check_apic(); > > + /* sanity check that the hardware exists or is emulated */ > + if (!check_hw_exists()) { > + pr_cont("no PMU driver, software events only.\n"); > + return; > + }
Maybe report something like this: "Broken PMU hardware detected, software events only."
Because this is really not something that's supposed to happen.
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