From: Andi Kleen <andi@firstfloor.org>
To: Eric Northup <digitaleric@google.com>
Cc: Andi Kleen <andi@firstfloor.org>,
Peter Zijlstra <peterz@infradead.org>,
gleb@kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
Stephane Eranian <eranian@google.com>, KVM <kvm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH 4/4] kvm: Implement PEBS virtualization
Date: Mon, 2 Jun 2014 21:57:11 +0200 [thread overview]
Message-ID: <20140602195711.GQ25366@two.firstfloor.org> (raw)
In-Reply-To: <CAG7+5M2h1_h2fW1KiD-ReXuxDe_EwmBUOJRwjgAvR79sUBxtgA@mail.gmail.com>
> It seems to me that with this patch, there is no way to expose a
> PMU-without-PEBS to the guest if the host has PEBS.
If you clear the CPUIDs then noone would ilikely access it.
But fair enough, I'll add extra checks for CPUID.
> 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.
BTW in practice it'll likely work anyways because many profilers
regularly re-set the PMU.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
next prev parent reply other threads:[~2014-06-02 19:57 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-30 1:12 Implement PEBS virtualization for Silvermont Andi Kleen
2014-05-30 1:12 ` [PATCH 1/4] perf: Add PEBS virtualization enable " Andi Kleen
2014-05-30 1:12 ` [PATCH 2/4] perf: Allow guest PEBS for KVM owned counters Andi Kleen
2014-05-30 7:31 ` Peter Zijlstra
2014-05-30 16:03 ` Andi Kleen
2014-05-30 16:17 ` Peter Zijlstra
2014-05-30 1:12 ` [PATCH 3/4] perf: Handle guest PEBS events with a fake event Andi Kleen
2014-05-30 7:34 ` Peter Zijlstra
2014-05-30 16:29 ` Andi Kleen
2014-05-30 1:12 ` [PATCH 4/4] kvm: Implement PEBS virtualization Andi Kleen
2014-05-30 8:21 ` Gleb Natapov
2014-05-30 16:24 ` Andi Kleen
2014-06-02 16:45 ` Gleb Natapov
2014-06-02 16:52 ` Andi Kleen
2014-06-02 19:09 ` Marcelo Tosatti
2014-06-02 19:05 ` Eric Northup
2014-06-02 19:57 ` Andi Kleen [this message]
2014-06-19 14:39 ` Paolo Bonzini
2014-06-10 18:04 ` Marcelo Tosatti
2014-06-10 19:22 ` Andi Kleen
2014-06-10 21:06 ` Marcelo Tosatti
2014-06-19 14:42 ` Paolo Bonzini
2014-06-19 17:33 ` Andi Kleen
2014-06-19 20:33 ` Paolo Bonzini
2014-06-22 13:57 ` Avi Kivity
2014-06-22 19:02 ` Andi Kleen
2014-06-24 16:45 ` Marcelo Tosatti
2014-06-25 7:04 ` Avi Kivity
2014-05-30 7:39 ` Implement PEBS virtualization for Silvermont Peter Zijlstra
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