From: Peter Zijlstra <peterz@infradead.org>
To: Manali Shukla <manali.shukla@amd.com>
Cc: Sean Christopherson <seanjc@google.com>,
Ingo Molnar <mingo@kernel.org>,
Dapeng Mi <dapeng1.mi@linux.intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Kan Liang <kan.liang@linux.intel.com>,
Like Xu <likexu@tencent.com>, Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
Ian Rogers <irogers@google.com>,
Adrian Hunter <adrian.hunter@intel.com>,
kvm@vger.kernel.org, linux-perf-users@vger.kernel.org,
linux-kernel@vger.kernel.org,
Zhenyu Wang <zhenyuw@linux.intel.com>,
Zhang Xiong <xiong.y.zhang@intel.com>,
Lv Zhiyuan <zhiyuan.lv@intel.com>,
Yang Weijiang <weijiang.yang@intel.com>,
Dapeng Mi <dapeng1.mi@intel.com>,
David Dunn <daviddunn@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Mingwei Zhang <mizhang@google.com>,
Jim Mattson <jmattson@google.com>,
Like Xu <like.xu.linux@gmail.com>
Subject: Re: [Patch v4 07/13] perf/x86: Add constraint for guest perf metrics event
Date: Wed, 11 Oct 2023 16:15:35 +0200 [thread overview]
Message-ID: <20231011141535.GF6307@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <03b7da03-78a1-95b1-3969-634b5c9a5a56@amd.com>
On Mon, Oct 09, 2023 at 10:33:41PM +0530, Manali Shukla wrote:
> Hi all,
>
> I would like to add following things to the discussion just for the awareness of
> everyone.
>
> Fully virtualized PMC support is coming to an upcoming AMD SoC and we are
> working on prototyping it.
>
> As part of virtualized PMC design, the PERF_CTL registers are defined as Swap
> type C: guest PMC states are loaded at VMRUN automatically but host PMC states
> are not saved by hardware.
Per the previous discussion, doing this while host has active counters
that do not have ::exclude_guest=1 is invalid and must result in an
error.
Also, I'm assuming it is all optional, a host can still profile a guest
if all is configured just so?
> If hypervisor is using the performance counters, it
> is hypervisor's responsibility to save PERF_CTL registers to host save area
> prior to VMRUN and restore them after VMEXIT.
Does VMEXIT clear global_ctrl at least?
> In order to tackle PMC overflow
> interrupts in guest itself, NMI virtualization or AVIC can be used, so that
> interrupt on PMC overflow in guest will not leak to host.
Can you please clarify -- AMD has this history with very dodgy PMI
boundaries. See the whole amd_pmu_adjust_nmi_window() crud. Even the
PMUv2 update didn't fix that nonsense.
How is any virt stuff supposed to fix this? If the hardware is late
delivering PMI, what guarantees a guest PMI does not land in host
context and vice-versa?
How does NMI virtualization (what even is that) or AVIC (I'm assuming
that's a virtual interrupt controller) help?
Please make very sure, with your hardware team, that PMI must not be
delivered after clearing global_ctrl (preferably) or at the very least,
there exists a sequence of operations that provides a hard barrier
to order PMI.
next prev parent reply other threads:[~2023-10-11 14:16 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-27 3:31 [Patch v4 00/13] Enable fixed counter 3 and topdown perf metrics for vPMU Dapeng Mi
2023-09-27 3:31 ` [Patch v4 01/13] KVM: x86/pmu: Add Intel CPUID-hinted TopDown slots event Dapeng Mi
2023-09-27 3:31 ` [Patch v4 02/13] KVM: x86/pmu: Support PMU fixed counter 3 Dapeng Mi
2023-09-27 3:31 ` [Patch v4 03/13] perf/core: Add function perf_event_group_leader_check() Dapeng Mi
2023-09-27 3:31 ` [Patch v4 04/13] perf/core: Add function perf_event_move_group() Dapeng Mi
2023-09-27 3:31 ` [Patch v4 05/13] perf/core: Add *group_leader for perf_event_create_group_kernel_counters() Dapeng Mi
2023-09-27 3:31 ` [Patch v4 06/13] perf/x86: Fix typos and inconsistent indents in perf_event header Dapeng Mi
2023-09-27 3:31 ` [Patch v4 07/13] perf/x86: Add constraint for guest perf metrics event Dapeng Mi
2023-09-27 11:33 ` Peter Zijlstra
2023-09-27 17:27 ` Sean Christopherson
2023-09-28 9:24 ` Mi, Dapeng
2023-09-29 11:53 ` Peter Zijlstra
2023-09-29 15:20 ` Ravi Bangoria
2023-10-02 12:29 ` Peter Zijlstra
2023-10-03 6:36 ` Ravi Bangoria
2023-09-29 15:46 ` Sean Christopherson
2023-09-30 3:29 ` Jim Mattson
2023-10-01 0:31 ` Namhyung Kim
2023-10-02 11:57 ` Peter Zijlstra
2023-10-02 13:30 ` Ingo Molnar
2023-10-02 15:23 ` David Dunn
2023-10-02 19:02 ` Mingwei Zhang
2023-10-02 15:56 ` Sean Christopherson
2023-10-02 19:50 ` Liang, Kan
2023-10-02 20:52 ` Peter Zijlstra
2023-10-02 20:40 ` Peter Zijlstra
2023-10-03 0:56 ` Sean Christopherson
2023-10-03 8:16 ` Peter Zijlstra
2023-10-03 15:23 ` Sean Christopherson
2023-10-03 18:21 ` Jim Mattson
2023-10-04 11:32 ` Peter Zijlstra
2023-10-04 11:21 ` Peter Zijlstra
2023-10-04 19:51 ` Mingwei Zhang
2023-10-04 21:50 ` Sean Christopherson
2023-10-04 22:05 ` Sean Christopherson
2023-10-08 10:04 ` Like Xu
2023-10-09 17:03 ` Manali Shukla
2023-10-11 14:15 ` Peter Zijlstra [this message]
2023-10-17 10:24 ` Manali Shukla
2023-10-17 16:58 ` Mingwei Zhang
2023-10-18 0:01 ` Mingwei Zhang
2023-10-11 14:20 ` Peter Zijlstra
2023-10-13 17:02 ` Sean Christopherson
2023-10-03 17:31 ` Manali Shukla
2023-10-03 22:02 ` Mingwei Zhang
2023-10-04 20:43 ` Sean Christopherson
2023-09-27 3:31 ` [Patch v4 08/13] perf/core: Add new function perf_event_topdown_metrics() Dapeng Mi
2023-09-27 3:31 ` [Patch v4 09/13] perf/x86/intel: Handle KVM virtual metrics event in perf system Dapeng Mi
2023-09-27 3:31 ` [Patch v4 10/13] KVM: x86/pmu: Extend pmc_reprogram_counter() to create group events Dapeng Mi
2023-09-27 3:31 ` [Patch v4 11/13] KVM: x86/pmu: Support topdown perf metrics feature Dapeng Mi
2023-09-27 3:31 ` [Patch v4 12/13] KVM: x86/pmu: Handle PERF_METRICS overflow Dapeng Mi
2023-09-27 3:31 ` [Patch v4 13/13] KVM: x86/pmu: Expose Topdown in MSR_IA32_PERF_CAPABILITIES Dapeng Mi
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