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Message-ID: <02c324f0-37e0-f58f-4572-a5967c2e54f1@intel.com>
Date: Fri, 6 Aug 2021 20:23:23 +0800
From: "Zhu, Lingshan" <lingshan.zhu@...el.com>
To: Liuxiangdong <liuxiangdong5@...wei.com>, peterz@...radead.org,
pbonzini@...hat.com
Cc: bp@...en8.de, seanjc@...gle.com, vkuznets@...hat.com,
wanpengli@...cent.com, jmattson@...gle.com, joro@...tes.org,
kan.liang@...ux.intel.com, ak@...ux.intel.com,
wei.w.wang@...el.com, eranian@...gle.com,
linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org,
like.xu.linux@...il.com, boris.ostrvsky@...cle.com,
Like Xu <like.xu@...ux.intel.com>
Subject: Re: [PATCH V9 03/18] perf/x86/intel: Handle guest PEBS overflow PMI
for KVM guest
On 8/5/2021 9:15 AM, Liuxiangdong wrote:
>
>
> On 2021/7/22 13:41, Zhu Lingshan wrote:
>> From: Like Xu <like.xu@...ux.intel.com>
>>
>> With PEBS virtualization, the guest PEBS records get delivered to the
>> guest DS, and the host pmi handler uses perf_guest_cbs->is_in_guest()
>> to distinguish whether the PMI comes from the guest code like Intel PT.
>>
>> No matter how many guest PEBS counters are overflowed, only triggering
>> one fake event is enough. The fake event causes the KVM PMI callback to
>> be called, thereby injecting the PEBS overflow PMI into the guest.
>>
>> KVM may inject the PMI with BUFFER_OVF set, even if the guest DS is
>> empty. That should really be harmless. Thus guest PEBS handler would
>> retrieve the correct information from its own PEBS records buffer.
>>
>> Originally-by: Andi Kleen <ak@...ux.intel.com>
>> Co-developed-by: Kan Liang <kan.liang@...ux.intel.com>
>> Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
>> Signed-off-by: Like Xu <like.xu@...ux.intel.com>
>> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
>> ---
>> arch/x86/events/intel/core.c | 45 ++++++++++++++++++++++++++++++++++++
>> 1 file changed, 45 insertions(+)
>>
>> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
>> index da835f5a37e2..2eceb73cd303 100644
>> --- a/arch/x86/events/intel/core.c
>> +++ b/arch/x86/events/intel/core.c
>> @@ -2783,6 +2783,50 @@ static void intel_pmu_reset(void)
>> }
>> DECLARE_STATIC_CALL(x86_guest_handle_intel_pt_intr,
>> *(perf_guest_cbs->handle_intel_pt_intr));
>> +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;
>
> guest_pebs_idxs has been defined here.
>
>> + struct perf_event *event = NULL;
>> + unsigned int guest = 0;
>> + int bit;
>> +
>> + guest = static_call(x86_guest_state)();
>> + if (!(guest & PERF_GUEST_ACTIVE))
>> + return;
>> +
>> + if (!x86_pmu.pebs_vmx || !x86_pmu.pebs_active ||
>> + !(cpuc->pebs_enabled & ~cpuc->intel_ctrl_host_mask))
>> + return;
>> +
> Why not use guest_pebs_idxs?
>
> + if (!x86_pmu.pebs_vmx || !x86_pmu.pebs_active ||
> + !guest_pebs_idxs)
> + return;
Thanks, I have apply this change in V10
Thanks
>
>
>> + for_each_set_bit(bit, (unsigned long *)&guest_pebs_idxs,
>> + INTEL_PMC_IDX_FIXED + x86_pmu.num_counters_fixed) {
>> + event = cpuc->events[bit];
>> + if (!event->attr.precise_ip)
>> + continue;
>> +
>> + perf_sample_data_init(data, 0, event->hw.last_period);
>> + if (perf_event_overflow(event, data, regs))
>> + x86_pmu_stop(event, 0);
>> +
>> + /* Inject one fake event is enough. */
>> + break;
>> + }
>> +}
>> static int handle_pmi_common(struct pt_regs *regs, u64 status)
>> {
>> @@ -2835,6 +2879,7 @@ static int handle_pmi_common(struct pt_regs
>> *regs, u64 status)
>> u64 pebs_enabled = cpuc->pebs_enabled;
>> handled++;
>> + x86_pmu_handle_guest_pebs(regs, &data);
>> x86_pmu.drain_pebs(regs, &data);
>> status &= intel_ctrl | GLOBAL_STATUS_TRACE_TOPAPMI;
>
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