Messages in this thread | | | Date | Mon, 2 Jun 2014 18:52:31 +0200 | From | Andi Kleen <> | Subject | Re: [PATCH 4/4] kvm: Implement PEBS virtualization |
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BTW I found some more problems in the v1 version.
> > > With EPT it is less likely to happen (but still possible IIRC depending on memory > > > pressure and how much memory shadow paging code is allowed to use), without EPT > > > it will happen for sure. > > > > Don't care about the non EPT case, this is white listed only for EPT supporting > > CPUs. > User may still disable EPT during module load, so pebs should be dropped > from a guest's cpuid in this case.
Ok.
> > > > > > There is nothing, as far as I can see, that says what will happen if the > > > condition is not met. I always interpreted it as undefined behaviour so > > > anything can happen including CPU dies completely. You are saying above > > > on one hand that CPU cannot handle any kinds of faults during write to > > > DS area, but on the other hand a guest could only crash itself. Is this > > > architecturally guarantied? > > > > You essentially would get random page faults, and the PEBS event will > > be cancelled. No hangs. > Is this a guest who will get those random page faults or a host?
The guest (on the white listed CPU models)
-Andi
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