Messages in this thread | | | Date | Mon, 25 Oct 2021 18:44:56 +0200 | Subject | Re: [PATCH] KVM: vPMU: Don't program counter for interrupt-based event sampling w/o lapic_in_kernel | From | Paolo Bonzini <> |
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On 25/10/21 18:31, Sean Christopherson wrote: >> vPMU depends on in-kernel lapic to deliver pmi interrupt, there is a >> lot of overhead when creating/maintaining perf_event object, >> locking/unlocking perf_event_ctx etc for vPMU. It silently fails to >> deliver pmi interrupt if w/o in-kernel lapic currently. Let's not >> program counter for interrupt-based event sampling w/o in-kernel >> lapic support to avoid the whole bothering. > > This feels all kinds of wrong. AFAIK, there's no way for KVM to enumerate to > the guest that the vPMU isn't capable of generating interrupts. I.e. any setup > that exposes a vPMU to the guest without an in-kernel local APIC is either > inherently broken or requires a paravirtualized guest. I don't think KVM's bugs > should be optimized.
Yeah, if it simplified the code it would be a different story, but here there's even not one but two new checks.
Paolo
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