Messages in this thread | | | Date | Tue, 07 Dec 2010 16:26:22 -0800 | From | Yinghai Lu <> | Subject | Re: perf hw in kexeced kernel broken in tip |
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On 12/07/2010 01:16 PM, Don Zickus wrote: > On Thu, Dec 02, 2010 at 08:34:30AM +0100, Peter Zijlstra wrote: >>> void __init lockup_detector_init(void) >>> { >>> void *cpu = (void *)(long)smp_processor_id(); >>> @@ -563,6 +576,7 @@ void __init lockup_detector_init(void) >>> >>> cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); >>> register_cpu_notifier(&cpu_nfb); >>> + register_reboot_notifier(&reboot_nfb); >>> >>> return; >>> } >> >> We'd really want a perf_event.c callback there to do as the hot-unplug >> code does and detach all running counters from the cpu. > > Ok, here is a simpler patch for now. > > --------------------------------8<-------- > From: Don Zickus <dzickus@redhat.com> > Date: Tue, 7 Dec 2010 16:06:59 -0500 > Subject: [PATCH] perf: Use event select bits for hardware check > > The counter registers can continue to increment if left enabled > across a kexec or a kdump. The makes the perf hardware check > accidentally return false when the hardware really does exist. > > Change the check to use the first bits of event selection. Those > bits should be safe as they are used to program the type of events > to use. And more importantly, they won't increment across kexec/kdump. > > Signed-off-by: Don Zickus <dzickus@redhat.com> > --- > arch/x86/kernel/cpu/perf_event.c | 8 ++++---- > 1 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c > index 7b91396..7d869c0 100644 > --- a/arch/x86/kernel/cpu/perf_event.c > +++ b/arch/x86/kernel/cpu/perf_event.c > @@ -377,10 +377,10 @@ static bool check_hw_exists(void) > u64 val, val_new = 0; > int ret = 0; > > - val = 0xabcdUL; > - ret |= checking_wrmsrl(x86_pmu.perfctr, val); > - ret |= rdmsrl_safe(x86_pmu.perfctr, &val_new); > - if (ret || val != val_new) > + val = 0xabUL; > + ret |= checking_wrmsrl(x86_pmu.eventsel, val); > + ret |= rdmsrl_safe(x86_pmu.eventsel, &val_new); > + if (ret || val != (val_new & 0xFF)) > return false; > > return true;
Thanks. it fixes the problem.
Yinghai
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