Messages in this thread | | | Subject | Re: [perf] fuzzer triggers unchecked MSR access error: WRMSR to 0x318 | From | Like Xu <> | Date | Mon, 2 Aug 2021 19:40:54 +0800 |
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On 29/7/2021 11:30 pm, Peter Zijlstra wrote: > 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.
I recently enabled guest BTS and encountered the same call trace.
For the proposal hybrid(cpuc->pmu, num_counters_fixed), Tested-by: Like Xu <likexu@tencent.com>
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