From: Peter Zijlstra <peterz@infradead.org>
To: "Xu, Like" <like.xu@intel.com>
Cc: Like Xu <like.xu@linux.intel.com>,
Kan Liang <kan.liang@linux.intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
eranian@google.com, kvm@vger.kernel.org,
Ingo Molnar <mingo@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Andi Kleen <andi@firstfloor.org>,
wei.w.wang@intel.com, luwei.kang@intel.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 04/17] perf: x86/ds: Handle guest PEBS overflow PMI and inject it to guest
Date: Fri, 15 Jan 2021 13:01:26 +0100 [thread overview]
Message-ID: <YAGEFgqQv281jVHc@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <9c343e40-bbdf-8af0-3307-5274070ee3d2@intel.com>
On Thu, Jan 14, 2021 at 11:39:00AM +0800, Xu, Like wrote:
> > Why do we need to? Can't we simply always forward the PMI if the guest
> > has bits set in MSR_IA32_PEBS_ENABLE ? Surely we can access the guest
> > MSRs at a reasonable rate..
> >
> > Sure, it'll send too many PMIs, but is that really a problem?
>
> More vPMI means more guest irq handler calls and
> more PMI virtualization overhead.
Only if you have both guest and host PEBS. And in that case I really
can't be arsed about some overhead to the guest.
> In addition,
> the correctness of some workloads (RR?) depends on
> the correct number of PMIs and the PMI trigger times
> and virt may not want to break this assumption.
Are you sure? Spurious NMI/PMIs are known to happen anyway. We have far
too much code to deal with them.
> > > + * If PEBS interrupt threshold on host is not exceeded in a NMI, there
> > > + * must be a PEBS overflow PMI generated from the guest PEBS counters.
> > > + * There is no ambiguity since the reported event in the PMI is guest
> > > + * only. It gets handled correctly on a case by case base for each event.
> > > + *
> > > + * Note: KVM disables the co-existence of guest PEBS and host PEBS.
> > Where; I need a code reference here.
>
> How about:
>
> Note: KVM will disable the co-existence of guest PEBS and host PEBS.
> In the intel_guest_get_msrs(), when we have host PEBS ctrl bit(s) enabled,
> KVM will clear the guest PEBS ctrl enable bit(s) before vm-entry.
> The guest PEBS users should be notified of this runtime restriction.
Since you had me look at that function, can clean up that
CONFIG_RETPOLINE crud and replace it with static_call() ?
next prev parent reply other threads:[~2021-01-15 12:03 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-04 13:15 [PATCH v3 00/17] KVM: x86/pmu: Add support to enable Guest PEBS via DS Like Xu
2021-01-04 13:15 ` [PATCH v3 01/17] KVM: x86/pmu: Set MSR_IA32_MISC_ENABLE_EMON bit when vPMU is enabled Like Xu
2021-01-04 13:15 ` [PATCH v3 02/17] KVM: x86/pmu: Use IA32_PERF_CAPABILITIES to adjust features visibility Like Xu
2021-01-04 13:15 ` [PATCH v3 03/17] KVM: x86/pmu: Introduce the ctrl_mask value for fixed counter Like Xu
2021-01-13 18:06 ` Peter Zijlstra
2021-01-14 1:58 ` Xu, Like
2021-01-04 13:15 ` [PATCH v3 04/17] perf: x86/ds: Handle guest PEBS overflow PMI and inject it to guest Like Xu
2021-01-13 18:22 ` Peter Zijlstra
2021-01-13 18:27 ` Peter Zijlstra
2021-01-14 3:39 ` Xu, Like
2021-01-15 12:01 ` Peter Zijlstra [this message]
2021-01-15 14:30 ` Xu, Like
2021-01-15 14:44 ` Peter Zijlstra
2021-01-15 15:12 ` Xu, Like
2021-01-25 8:26 ` Like Xu
2021-01-25 11:47 ` Peter Zijlstra
2021-02-02 6:31 ` Xu, Like
2021-01-14 18:55 ` Sean Christopherson
2021-01-15 2:49 ` Xu, Like
2021-01-15 17:42 ` Sean Christopherson
2021-01-22 5:30 ` Like Xu
2021-01-04 13:15 ` [PATCH v3 05/17] KVM: x86/pmu: Reprogram guest PEBS event to emulate guest PEBS counter Like Xu
2021-01-15 11:33 ` Peter Zijlstra
2021-01-15 13:53 ` Xu, Like
2021-01-04 13:15 ` [PATCH v3 06/17] KVM: x86/pmu: Add IA32_PEBS_ENABLE MSR emulation for extended PEBS Like Xu
2021-01-05 21:11 ` Sean Christopherson
2021-01-07 12:38 ` Xu, Like
2021-01-15 14:46 ` Peter Zijlstra
2021-01-15 15:29 ` Xu, Like
2021-01-04 13:15 ` [PATCH v3 07/17] KVM: x86/pmu: Add IA32_DS_AREA MSR emulation to manage guest DS buffer Like Xu
2021-01-05 21:16 ` Sean Christopherson
2021-01-08 3:05 ` Xu, Like
2021-01-04 13:15 ` [PATCH v3 08/17] KVM: x86/pmu: Add PEBS_DATA_CFG MSR emulation to support adaptive PEBS Like Xu
2021-01-04 13:15 ` [PATCH v3 09/17] KVM: x86: Set PEBS_UNAVAIL in IA32_MISC_ENABLE when PEBS is enabled Like Xu
2021-01-04 13:15 ` [PATCH v3 10/17] KVM: x86/pmu: Expose CPUIDs feature bits PDCM, DS, DTES64 Like Xu
2021-01-04 13:15 ` [PATCH v3 11/17] KVM: x86/pmu: Adjust precise_ip to emulate Ice Lake guest PDIR counter Like Xu
2021-01-04 13:15 ` [PATCH v3 12/17] KVM: x86/pmu: Disable guest PEBS when counters are cross-mapped Like Xu
2021-01-04 13:15 ` [PATCH v3 13/17] KVM: x86/pmu: Add hook to emulate pebs for cross-mapped counters Like Xu
2021-01-04 13:15 ` [PATCH v3 14/17] KVM: vmx/pmu: Limit pebs_interrupt_threshold in the guest DS area Like Xu
2021-01-04 13:15 ` [PATCH v3 15/17] KVM: vmx/pmu: Rewrite applicable_counters field in guest PEBS records Like Xu
2021-01-04 13:15 ` [PATCH v3 16/17] KVM: x86/pmu: Save guest pebs reset values when pebs is configured Like Xu
2021-01-04 13:15 ` [PATCH v3 17/17] KVM: x86/pmu: Adjust guest pebs reset values for crpss-mapped counters Like Xu
2021-01-14 19:10 ` [PATCH v3 00/17] KVM: x86/pmu: Add support to enable Guest PEBS via DS Sean Christopherson
2021-01-15 2:02 ` Xu, Like
2021-01-15 17:57 ` Sean Christopherson
2021-01-15 18:27 ` Andi Kleen
2021-01-15 18:51 ` Sean Christopherson
2021-01-15 19:11 ` Andi Kleen
2021-01-22 9:56 ` Peter Zijlstra
2021-01-25 8:08 ` Like Xu
2021-01-25 11:13 ` Peter Zijlstra
2021-01-25 12:07 ` Xu, Like
2021-01-25 12:18 ` Peter Zijlstra
2021-01-25 12:53 ` Xu, Like
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