From: David Dunn <daviddunn@google.com>
To: "Liang, Kan" <kan.liang@linux.intel.com>
Cc: Jim Mattson <jmattson@google.com>,
Dave Hansen <dave.hansen@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Like Xu <like.xu.linux@gmail.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Like Xu <likexu@tencent.com>,
Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH kvm/queue v2 2/3] perf: x86/core: Add interface to query perfmon_event_map[] directly
Date: Thu, 10 Feb 2022 11:55:45 -0800 [thread overview]
Message-ID: <CABOYuvZ9SZAWeRkrhhhpMM4XwzMzXv9A1WDpc6z8SUBquf0SFQ@mail.gmail.com> (raw)
In-Reply-To: <d86ba87b-d98a-53a0-b2cd-5bf77b97b592@linux.intel.com>
Kan,
On Thu, Feb 10, 2022 at 11:46 AM Liang, Kan <kan.liang@linux.intel.com> wrote:
> No, we don't, at least for Linux. Because the host own everything. It
> doesn't need the MSR to tell which one is in use. We track it in an SW way.
>
> For the new request from the guest to own a counter, I guess maybe it is
> worth implementing it. But yes, the existing/legacy guest never check
> the MSR.
This is the expectation of all software that uses the PMU in every
guest. It isn't just the Linux perf system.
The KVM vPMU model we have today results in the PMU utilizing software
simply not working properly in a guest. The only case that can
consistently "work" today is not giving the guest a PMU at all.
And that's why you are hearing requests to gift the entire PMU to the
guest while it is running. All existing PMU software knows about the
various constraints on exactly how each MSR must be used to get sane
data. And by gifting the entire PMU it allows that software to work
properly. But that has to be controlled by policy at host level such
that the owner of the host knows that they are not going to have PMU
visibility into guests that have control of PMU.
Dave Dunn
next prev parent reply other threads:[~2022-02-10 19:56 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-17 8:53 [PATCH kvm/queue v2 0/3] KVM: x86/pmu: Fix out-of-date AMD amd_event_mapping[] Like Xu
2022-01-17 8:53 ` [PATCH kvm/queue v2 1/3] KVM: x86/pmu: Replace pmu->available_event_types with a new BITMAP Like Xu
2022-02-01 12:26 ` Paolo Bonzini
2022-01-17 8:53 ` [PATCH kvm/queue v2 2/3] perf: x86/core: Add interface to query perfmon_event_map[] directly Like Xu
2022-02-01 12:27 ` Paolo Bonzini
2022-02-02 14:43 ` Peter Zijlstra
2022-02-02 22:35 ` Jim Mattson
2022-02-03 17:33 ` David Dunn
2022-02-09 8:10 ` KVM: x86: Reconsider the current approach of vPMU Like Xu
2022-02-09 13:33 ` Peter Zijlstra
2022-02-09 21:00 ` Sean Christopherson
2022-02-10 12:08 ` Like Xu
2022-02-10 17:12 ` Sean Christopherson
2022-02-16 3:33 ` Like Xu
2022-02-16 17:53 ` Jim Mattson
2022-02-09 13:21 ` [PATCH kvm/queue v2 2/3] perf: x86/core: Add interface to query perfmon_event_map[] directly Peter Zijlstra
2022-02-09 15:40 ` Dave Hansen
2022-02-09 18:47 ` Jim Mattson
2022-02-09 18:57 ` Dave Hansen
2022-02-09 19:24 ` David Dunn
2022-02-10 13:29 ` Like Xu
2022-02-10 15:34 ` Liang, Kan
2022-02-10 16:34 ` Jim Mattson
2022-02-10 18:30 ` Liang, Kan
2022-02-10 19:16 ` Jim Mattson
2022-02-10 19:46 ` Liang, Kan
2022-02-10 19:55 ` David Dunn [this message]
2022-02-11 14:11 ` Liang, Kan
2022-02-11 18:08 ` Jim Mattson
2022-02-11 21:47 ` Liang, Kan
2022-02-12 23:31 ` Jim Mattson
2022-02-14 21:55 ` Liang, Kan
2022-02-14 22:55 ` Jim Mattson
2022-02-16 7:36 ` Like Xu
2022-02-16 18:10 ` Jim Mattson
2022-02-16 7:30 ` Like Xu
2022-02-16 5:08 ` Like Xu
2022-02-10 12:55 ` Like Xu
2022-02-12 23:32 ` Jim Mattson
2022-02-08 11:52 ` Like Xu
2022-01-17 8:53 ` [PATCH kvm/queue v2 3/3] KVM: x86/pmu: Setup the {inte|amd}_event_mapping[] when hardware_setup Like Xu
2022-02-01 12:28 ` Paolo Bonzini
2022-02-08 10:10 ` Like Xu
2022-01-26 11:22 ` [PATCH kvm/queue v2 0/3] KVM: x86/pmu: Fix out-of-date AMD amd_event_mapping[] Like Xu
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