From: Like Xu <like.xu@linux.intel.com>
To: Sean Christopherson <seanjc@google.com>,
Peter Zijlstra <peterz@infradead.org>
Cc: Kan Liang <kan.liang@linux.intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
eranian@google.com, kvm@vger.kernel.org,
Ingo Molnar <mingo@redhat.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, 22 Jan 2021 13:30:20 +0800 [thread overview]
Message-ID: <9fa07da4-8ef4-f1f2-72a0-5d747e283912@linux.intel.com> (raw)
In-Reply-To: <YAHT+zLiIg/oUygZ@google.com>
On 2021/1/16 1:42, Sean Christopherson wrote:
> On Fri, Jan 15, 2021, Xu, Like wrote:
>> On 2021/1/15 2:55, Sean Christopherson wrote:
>>> On Mon, Jan 04, 2021, Like Xu wrote:
>>>> + * Note: KVM disables the co-existence of guest PEBS and host PEBS.
>>> By "KVM", do you mean KVM's loading of the MSRs provided by intel_guest_get_msrs()?
>>> Because the PMU should really be the entity that controls guest vs. host. KVM
>>> should just be a dumb pipe that handles the mechanics of how values are context
>>> switch.
>>
>> The intel_guest_get_msrs() and atomic_switch_perf_msrs()
>> will work together to disable the co-existence of guest PEBS and host PEBS:
>>
>> https://lore.kernel.org/kvm/961e6135-ff6d-86d1-3b7b-a1846ad0e4c4@intel.com/
>>
>> +
>>
>> static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx)
>> ...
>> if (nr_msrs > 2 && (msrs[1].guest & msrs[0].guest)) {
>> msrs[2].guest = pmu->ds_area;
>> if (nr_msrs > 3)
>> msrs[3].guest = pmu->pebs_data_cfg;
>> }
>>
>> for (i = 0; i < nr_msrs; i++)
>> ...
>
> Yeah, that's exactly what I'm complaining about. Splitting the logic for
> determining the guest values is unnecessarily confusing, and as evidenced by the
> PEBS_ENABLE bug, potentially fragile. Perf should have full knowledge and
> control of what values are loaded for the guest. And, the above indexing magic
> is nigh impossible to follow and _super_ fragile.
Thanks for pointing this out.
>
> If we change .guest_get_msrs() to take a struct kvm_pmu pointer, then it can
> generate the full set of guest values by grabbing ds_area and pebs_data_cfg.
> Alternatively, .guest_get_msrs() could take the desired guest MSR values
> directly (ds_area and pebs_data_cfg), but kvm_pmu is vendor agnostic, so I don't
> see any reason to not just pass the pointer.
Hi Peter,
What do you think of us passing a "struct kvm_pmu" pointer (defined in
arch/x86/include/asm/kvm_host.h) to guest_get_msrs(int *nr) ?
---
thx,likexu
next prev parent reply other threads:[~2021-01-22 5:32 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
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 [this message]
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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