linux-kernel - Re: [PATCH v14 00/11] KVM: x86/pmu: Guest Last Branch Recording Enabling

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Date:   Thu, 29 Jul 2021 20:40:05 +0800
From:   Liuxiangdong <liuxiangdong5@...wei.com>
To:     <like.xu@...ux.intel.com>
CC:     <ak@...ux.intel.com>, <alex.shi@...ux.alibaba.com>,
        <jmattson@...gle.com>, <joro@...tes.org>, <kan.liang@...el.com>,
        <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <pbonzini@...hat.com>, <seanjc@...gle.com>, <vkuznets@...hat.com>,
        <wanpengli@...cent.com>, <wei.w.wang@...el.com>, <x86@...nel.org>,
        "Fangyi (Eric)" <eric.fangyi@...wei.com>,
        Xiexiangyou <xiexiangyou@...wei.com>
Subject: Re: [PATCH v14 00/11] KVM: x86/pmu: Guest Last Branch Recording
 Enabling

Hi, like.

This patch set has been merged in 5.12 kernel tree so we can use LBR in 
Guest.
Does it have requirement on CPU?
I can use lbr in guest on skylake and icelake, but cannot on IvyBridge.

I can see lbr formats(000011b) in perf_capabilities msr(0x345), but 
there is still
error when I try.

$ perf record -b
Error:
cycles: PMU Hardware doesn't support sampling/overflow-interrupts. Try 
'perf stat'

Host CPU:
Architecture:                    x86_64
CPU op-mode(s):                  32-bit, 64-bit
Byte Order:                      Little Endian
Address sizes:                   46 bits physical, 48 bits virtual
CPU(s):                          24
On-line CPU(s) list:             0-23
Thread(s) per core:              2
Core(s) per socket:              6
Socket(s):                       2
NUMA node(s):                    2
Vendor ID:                       GenuineIntel
CPU family:                      6
Model:                           62
Model name:                      Intel(R) Xeon(R) CPU E5-2620 v2 @ 2.10GHz
Stepping:                        4


Thanks!
Xiangdong Liu