From: "Liang, Kan" <kan.liang@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>, Luwei Kang <luwei.kang@intel.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, mingo@redhat.com, acme@kernel.org,
mark.rutland@arm.com, alexander.shishkin@linux.intel.com,
jolsa@redhat.com, namhyung@kernel.org, tglx@linutronix.de,
bp@alien8.de, hpa@zytor.com, pbonzini@redhat.com,
sean.j.christopherson@intel.com, vkuznets@redhat.com,
wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org,
pawan.kumar.gupta@linux.intel.com, ak@linux.intel.com,
thomas.lendacky@amd.com, fenghua.yu@intel.com,
like.xu@linux.intel.com
Subject: Re: [PATCH v1 01/11] perf/x86/core: Support KVM to assign a dedicated counter for guest PEBS
Date: Fri, 6 Mar 2020 09:42:47 -0500 [thread overview]
Message-ID: <b72cb68e-1a0a-eeff-21b4-ce412e939cfd@linux.intel.com> (raw)
In-Reply-To: <20200306135317.GD12561@hirez.programming.kicks-ass.net>
On 3/6/2020 8:53 AM, Peter Zijlstra wrote:
> On Fri, Mar 06, 2020 at 01:56:55AM +0800, Luwei Kang wrote:
>> From: Kan Liang <kan.liang@linux.intel.com>
>>
>> The PEBS event created by host needs to be assigned specific counters
>> requested by the guest, which means the guest and host counter indexes
>> have to be the same or fail to create. This is needed because PEBS leaks
>> counter indexes into the guest. Otherwise, the guest driver will be
>> confused by the counter indexes in the status field of the PEBS record.
>>
>> A guest_dedicated_idx field is added to indicate the counter index
>> specifically requested by KVM. The dedicated event constraints would
>> constrain the counter in the host to the same numbered counter in guest.
>>
>> A intel_ctrl_guest_dedicated_mask field is added to indicate the enabled
>> counters for guest PEBS events. The IA32_PEBS_ENABLE MSR will be switched
>> during the VMX transitions if intel_ctrl_guest_owned is set.
>>
>
>> + /* the guest specified counter index of KVM owned event, e.g PEBS */
>> + int guest_dedicated_idx;
>
> We've always objected to guest 'owned' counters, they destroy scheduling
> freedom. Why are you expecting that to be any different this time?
>
The new proposal tries to 'own' a counter by setting the event
constraint. It doesn't stop other events using the counter.
If there is high priority event which requires the same counter,
scheduler can still reject the request from KVM.
I don't think it destroys the scheduling freedom this time.
Thanks,
Kan
next prev parent reply other threads:[~2020-03-06 14:43 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-05 17:56 [PATCH v1 00/11] PEBS virtualization enabling via DS Luwei Kang
2020-03-05 16:51 ` Paolo Bonzini
2020-03-05 17:56 ` [PATCH v1 01/11] perf/x86/core: Support KVM to assign a dedicated counter for guest PEBS Luwei Kang
2020-03-06 13:53 ` Peter Zijlstra
2020-03-06 14:42 ` Liang, Kan [this message]
2020-03-09 10:04 ` Peter Zijlstra
2020-03-09 13:12 ` Liang, Kan
2020-03-09 15:05 ` Peter Zijlstra
2020-03-09 19:28 ` Liang, Kan
2020-03-12 10:28 ` Kang, Luwei
2020-03-26 14:03 ` Liang, Kan
2020-04-07 12:34 ` Kang, Luwei
2020-06-12 5:28 ` Kang, Luwei
2020-06-19 9:30 ` Kang, Luwei
2020-08-20 3:32 ` Like Xu
2020-03-09 15:44 ` Andi Kleen
2020-03-05 17:56 ` [PATCH v1 02/11] perf/x86/ds: Handle guest PEBS events overflow and inject fake PMI Luwei Kang
2020-03-05 17:56 ` [PATCH v1 03/11] perf/x86: Expose a function to disable auto-reload Luwei Kang
2020-03-05 17:56 ` [PATCH v1 04/11] KVM: x86/pmu: Decouple event enablement from event creation Luwei Kang
2020-03-05 17:56 ` [PATCH v1 05/11] KVM: x86/pmu: Add support to reprogram PEBS event for guest counters Luwei Kang
2020-03-06 16:28 ` kbuild test robot
2020-03-09 0:58 ` Xu, Like
2020-03-05 17:57 ` [PATCH v1 06/11] KVM: x86/pmu: Implement is_pebs_via_ds_supported pmu ops Luwei Kang
2020-03-05 17:57 ` [PATCH v1 07/11] KVM: x86/pmu: Expose CPUIDs feature bits PDCM, DS, DTES64 Luwei Kang
2020-03-05 17:57 ` [PATCH v1 08/11] KVM: x86/pmu: PEBS MSRs emulation Luwei Kang
2020-03-05 17:57 ` [PATCH v1 09/11] KVM: x86/pmu: Expose PEBS feature to guest Luwei Kang
2020-03-05 17:57 ` [PATCH v1 10/11] KVM: x86/pmu: Introduce the mask value for fixed counter Luwei Kang
2020-03-05 17:57 ` [PATCH v1 11/11] KVM: x86/pmu: Adaptive PEBS virtualization enabling Luwei Kang
2020-03-05 22:48 ` [PATCH v1 00/11] PEBS virtualization enabling via DS Andi Kleen
2020-03-06 5:37 ` Kang, Luwei
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