From: Peter Zijlstra <peterz@infradead.org>
To: Jim Mattson <jmattson@google.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>,
Mingwei Zhang <mizhang@google.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [Patch v4 07/13] perf/x86: Add constraint for guest perf metrics event
Date: Wed, 4 Oct 2023 13:32:50 +0200 [thread overview]
Message-ID: <20231004113250.GB5947@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <CALMp9eRew1+-gDy36m3qWy9D9TQP+mkzPQg=xowKcaG+NpbX0w@mail.gmail.com>
On Tue, Oct 03, 2023 at 11:21:46AM -0700, Jim Mattson wrote:
> On Tue, Oct 3, 2023 at 8:23 AM Sean Christopherson <seanjc@google.com> wrote:
> > > Since you steal the whole PMU, can't you re-route the PMI to something
> > > that's virt friendly too?
> >
> > Hmm, actually, we probably could. It would require modifying the host's APIC_LVTPC
> > entry when context switching the PMU, e.g. to replace the NMI with a dedicated IRQ
> > vector. As gross as that sounds, it might actually be cleaner overall than
> > deciphering whether an NMI belongs to the host or guest, and it would almost
> > certainly yield lower latency for guest PMIs.
>
> Ugh. Can't KVM just install its own NMI handler? Either way, it's
> possible for late PMIs to arrive in the wrong context.
I don't think you realize what a horrible trainwreck the NMI handler is.
Every handler has to be able to determine if the NMI is theirs to
handle.
If we go do this whole swizzle thing we must find a sequence of PMU
'instructions' that syncs against the PMI, because otherwise we're going
to loose PMIs and that's going to be a *TON* of pain.
I'll put it on the agenda for the next time I talk with the hardware
folks. But IIRC the AMD thing is *much* worse in this regards than the
Intel one.
next prev parent reply other threads:[~2023-10-04 11:33 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 [this message]
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
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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