linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: "Zhu, Lingshan" <lingshan.zhu@intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: pbonzini@redhat.com, bp@alien8.de, seanjc@google.com,
	vkuznets@redhat.com, wanpengli@tencent.com, jmattson@google.com,
	joro@8bytes.org, weijiang.yang@intel.com,
	kan.liang@linux.intel.com, ak@linux.intel.com,
	wei.w.wang@intel.com, eranian@google.com,
	liuxiangdong5@huawei.com, linux-kernel@vger.kernel.org,
	x86@kernel.org, kvm@vger.kernel.org, like.xu.linux@gmail.com,
	Like Xu <like.xu@linux.intel.com>
Subject: Re: [PATCH V7 03/18] perf/x86/intel: Handle guest PEBS overflow PMI for KVM guest
Date: Thu, 8 Jul 2021 21:39:50 +0800	[thread overview]
Message-ID: <1ee16a88-3de6-759c-db9e-ce2f3b6993b0@intel.com> (raw)
In-Reply-To: <YN74d+LwFbwO75N3@hirez.programming.kicks-ass.net>



On 7/2/2021 7:28 PM, Peter Zijlstra wrote:
> On Tue, Jun 22, 2021 at 05:42:51PM +0800, Zhu Lingshan wrote:
>> +DECLARE_STATIC_CALL(x86_guest_state, *(perf_guest_cbs->state));
>> +
>> +/*
>> + * We may be running with guest PEBS events created by KVM, and the
>> + * PEBS records are logged into the guest's DS and invisible to host.
>> + *
>> + * In the case of guest PEBS overflow, we only trigger a fake event
>> + * to emulate the PEBS overflow PMI for guest PBES counters in KVM.
>> + * The guest will then vm-entry and check the guest DS area to read
>> + * the guest PEBS records.
>> + *
>> + * The contents and other behavior of the guest event do not matter.
>> + */
>> +static void x86_pmu_handle_guest_pebs(struct pt_regs *regs,
>> +				      struct perf_sample_data *data)
>> +{
>> +	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
>> +	u64 guest_pebs_idxs = cpuc->pebs_enabled & ~cpuc->intel_ctrl_host_mask;
>> +	struct perf_event *event = NULL;
>> +	unsigned int guest = 0;
>> +	int bit;
>> +
>> +	if (!x86_pmu.pebs_vmx || !x86_pmu.pebs_active ||
>> +	    !(cpuc->pebs_enabled & ~cpuc->intel_ctrl_host_mask))
>> +		return;
>> +
>> +	guest = static_call(x86_guest_state)();
>> +	if (!(guest & PERF_GUEST_ACTIVE))
>> +		return;
> I think you've got the branches the wrong way around here; nobody runs a
> VM so this branch will get you out without a load.
>
> Only if you're one of those daft people running a VM, are you interested
> in any of the other conditions that are required.
>
> Also, I think both pebs_active and pebs_vmx can he a static_branch, but
> that can be done later I suppose.
Hi Peter,

If I understand this correctly, are you suggesting we put "if (!(guest & 
PERF_GUEST_ACTIVE))" first because this is a lower cost branch?

Thanks,
Zhu Lingshan


  reply	other threads:[~2021-07-08 13:39 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-22  9:42 [PATCH V7 00/18] KVM: x86/pmu: Add *basic* support to enable guest PEBS via DS Zhu Lingshan
2021-06-22  9:42 ` [PATCH V7 01/18] perf/core: Use static_call to optimize perf_guest_info_callbacks Zhu Lingshan
2021-07-02 11:22   ` Peter Zijlstra
2021-07-02 16:00     ` Joe Perches
2021-07-02 16:19       ` Peter Zijlstra
2021-07-02 16:42         ` Joe Perches
2021-07-02 16:38       ` Mark Rutland
2021-07-02 16:56         ` Joe Perches
2021-07-08  8:53     ` Zhu Lingshan
2021-06-22  9:42 ` [PATCH V7 02/18] perf/x86/intel: Add EPT-Friendly PEBS for Ice Lake Server Zhu Lingshan
2021-06-22  9:42 ` [PATCH V7 03/18] perf/x86/intel: Handle guest PEBS overflow PMI for KVM guest Zhu Lingshan
2021-07-02 11:28   ` Peter Zijlstra
2021-07-08 13:39     ` Zhu, Lingshan [this message]
2021-06-22  9:42 ` [PATCH V7 04/18] perf/x86/core: Pass "struct kvm_pmu *" to determine the guest values Zhu Lingshan
2021-06-22  9:42 ` [PATCH V7 05/18] KVM: x86/pmu: Set MSR_IA32_MISC_ENABLE_EMON bit when vPMU is enabled Zhu Lingshan
2021-06-22  9:42 ` [PATCH V7 06/18] KVM: x86/pmu: Introduce the ctrl_mask value for fixed counter Zhu Lingshan
2021-06-22  9:42 ` [PATCH V7 07/18] x86/perf/core: Add pebs_capable to store valid PEBS_COUNTER_MASK value Zhu Lingshan
2021-06-22  9:42 ` [PATCH V7 08/18] KVM: x86/pmu: Add IA32_PEBS_ENABLE MSR emulation for extended PEBS Zhu Lingshan
2021-06-22  9:42 ` [PATCH V7 09/18] KVM: x86/pmu: Reprogram PEBS event to emulate guest PEBS counter Zhu Lingshan
2021-06-22  9:42 ` [PATCH V7 10/18] KVM: x86/pmu: Adjust precise_ip to emulate Ice Lake guest PDIR counter Zhu Lingshan
2021-06-22  9:42 ` [PATCH V7 11/18] KVM: x86/pmu: Add IA32_DS_AREA MSR emulation to support guest DS Zhu Lingshan
2021-07-02 11:52   ` Peter Zijlstra
2021-07-08  8:52     ` Zhu, Lingshan
2021-06-22  9:43 ` [PATCH V7 12/18] KVM: x86/pmu: Add PEBS_DATA_CFG MSR emulation to support adaptive PEBS Zhu Lingshan
2021-06-22  9:43 ` [PATCH V7 13/18] KVM: x86: Set PEBS_UNAVAIL in IA32_MISC_ENABLE when PEBS is enabled Zhu Lingshan
2021-06-22  9:43 ` [PATCH V7 14/18] KVM: x86/pmu: Move pmc_speculative_in_use() to arch/x86/kvm/pmu.h Zhu Lingshan
2021-06-22  9:43 ` [PATCH V7 15/18] KVM: x86/pmu: Disable guest PEBS temporarily in two rare situations Zhu Lingshan
2021-07-02 12:46   ` Peter Zijlstra
2021-07-08  8:52     ` Zhu, Lingshan
2021-06-22  9:43 ` [PATCH V7 16/18] KVM: x86/pmu: Add kvm_pmu_cap to optimize perf_get_x86_pmu_capability Zhu Lingshan
2021-06-22  9:43 ` [PATCH V7 17/18] KVM: x86/cpuid: Refactor host/guest CPU model consistency check Zhu Lingshan
2021-06-22  9:43 ` [PATCH V7 18/18] KVM: x86/pmu: Expose CPUIDs feature bits PDCM, DS, DTES64 Zhu Lingshan
2021-06-25  9:40 ` [PATCH V7 00/18] KVM: x86/pmu: Add *basic* support to enable guest PEBS via DS Liuxiangdong
2021-06-25  9:46   ` Zhu, Lingshan
2021-06-28  7:49     ` Wang, Wei W
2021-06-28  7:53       ` Zhu, Lingshan
2021-07-02 12:49 ` Peter Zijlstra
2021-07-12  1:37 ` Liuxiangdong
2021-07-12 10:34   ` Like Xu

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1ee16a88-3de6-759c-db9e-ce2f3b6993b0@intel.com \
    --to=lingshan.zhu@intel.com \
    --cc=ak@linux.intel.com \
    --cc=bp@alien8.de \
    --cc=eranian@google.com \
    --cc=jmattson@google.com \
    --cc=joro@8bytes.org \
    --cc=kan.liang@linux.intel.com \
    --cc=kvm@vger.kernel.org \
    --cc=like.xu.linux@gmail.com \
    --cc=like.xu@linux.intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=liuxiangdong5@huawei.com \
    --cc=pbonzini@redhat.com \
    --cc=peterz@infradead.org \
    --cc=seanjc@google.com \
    --cc=vkuznets@redhat.com \
    --cc=wanpengli@tencent.com \
    --cc=wei.w.wang@intel.com \
    --cc=weijiang.yang@intel.com \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).