Messages in this thread | | | Date | Fri, 30 Jun 2023 17:21:24 +0200 | From | Roman Kagan <> | Subject | Re: [PATCH] KVM: x86: vPMU: truncate counter value to allowed width |
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On Fri, Jun 30, 2023 at 07:28:29AM -0700, Sean Christopherson wrote: > On Fri, Jun 30, 2023, Roman Kagan wrote: > > On Thu, Jun 29, 2023 at 05:11:06PM -0700, Sean Christopherson wrote: > > > @@ -74,6 +74,14 @@ static inline u64 pmc_read_counter(struct kvm_pmc *pmc) > > > return counter & pmc_bitmask(pmc); > > > } > > > > > > +static inline void pmc_write_counter(struct kvm_pmc *pmc, u64 val) > > > +{ > > > + if (pmc->perf_event && !pmc->is_paused) > > > + perf_event_set_count(pmc->perf_event, val); > > > + > > > + pmc->counter = val; > > > > Doesn't this still have the original problem of storing wider value than > > allowed? > > Yes, this was just to fix the counter offset weirdness. My plan is to apply your > patch on top. Sorry for not making that clear.
Ah, got it, thanks!
Also I'm now chasing a problem that we occasionally see
[3939579.462832] Uhhuh. NMI received for unknown reason 30 on CPU 43. [3939579.462836] Do you have a strange power saving mode enabled? [3939579.462836] Dazed and confused, but trying to continue
in the guests when perf is used. These messages disappear when 9cd803d496e7 ("KVM: x86: Update vPMCs when retiring instructions") is reverted. I haven't yet figured out where exactly the culprit is.
Thanks, Roman.
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