linux-kernel - Re: [PATCH 4/4] kvm: Implement PEBS virtualization

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Date:	Thu, 19 Jun 2014 16:39:57 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Andi Kleen <andi@...stfloor.org>,
	Eric Northup <digitaleric@...gle.com>
CC:	Peter Zijlstra <peterz@...radead.org>, gleb@...nel.org,
	Stephane Eranian <eranian@...gle.com>,
	KVM <kvm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 4/4] kvm: Implement PEBS virtualization

Il 02/06/2014 21:57, Andi Kleen ha scritto:
> > It would be a bigger concern if we expected virtual PMU migration to
> > work, but I think it would be nice to update kvm_pmu_cpuid_update() to
> > notice the presence/absence of the new CPUID bits, and then store that
> > into per-VM kvm_pmu->pebs_allowed rather than relying only on the
> > per-host perf_pebs_virtualization().
>
> I hope at some point it can work. There shouldn't be any problems
> with migrating to the same CPU model, in many cases (same event
> and same PEBS format) it'll likely even work between models or
> gracefully degrade.

The code is there in both kernel and QEMU, it's just very little tested.

Paolo
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