Messages in this thread | | | Date | Thu, 29 Jul 2021 17:30:12 +0200 | From | Peter Zijlstra <> | Subject | Re: [perf] fuzzer triggers unchecked MSR access error: WRMSR to 0x318 |
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On Thu, Jul 29, 2021 at 09:21:01AM -0400, Liang, Kan wrote: > > > On 7/29/2021 5:14 AM, Peter Zijlstra wrote: > > On Wed, Jul 28, 2021 at 12:49:43PM -0400, Vince Weaver wrote: > > > [32694.087403] unchecked MSR access error: WRMSR to 0x318 (tried to write 0x0000000000000000) at rIP: 0xffffffff8106f854 (native_write_msr+0x4/0x20) > > > [32694.101374] Call Trace: > > > [32694.103974] perf_clear_dirty_counters+0x86/0x100 > > > > Hmm.. if I read this right that's MSR_ARCH_PERFMON_FIXED_CTR0 + i, given > > that FIXED_CTR0 is 0x309 that gives i == 15, which is FIXED_BTS. > > > > I'm thinking something like this ought to cure things. > > > > --- > > arch/x86/events/core.c | 12 +++++++----- > > 1 file changed, 7 insertions(+), 5 deletions(-) > > > > diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c > > index 1eb45139fcc6..04edf8017961 100644 > > --- a/arch/x86/events/core.c > > +++ b/arch/x86/events/core.c > > @@ -2489,13 +2489,15 @@ void perf_clear_dirty_counters(void) > > return; > > for_each_set_bit(i, cpuc->dirty, X86_PMC_IDX_MAX) { > > - /* Metrics and fake events don't have corresponding HW counters. */ > > - if (is_metric_idx(i) || (i == INTEL_PMC_IDX_FIXED_VLBR)) > > - continue; > > - else if (i >= INTEL_PMC_IDX_FIXED) > > + if (i >= INTEL_PMC_IDX_FIXED) { > > + /* Metrics and fake events don't have corresponding HW counters. */ > > + if ((i - INTEL_PMC_IDX_FIXED) >= x86_pmu.num_counters_fixed) > > Yes, the fix is better. My previous implementation tries to pick up all the > special cases. It's very likely to miss some special cases like FIXED_BTS > and probably any new fake events added later if there are. > Thanks for the fix. > > The x86_pmu.num_counters_fixed should work well on HSW. But we have hybrid > machines now. I think we can use > hybrid(cpuc->pmu, num_counters_fixed) instead, which should be more > accurate.
Yes, good point. I guess I still need to adjust to the hybrid world.
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