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Subject: Re: [PATCH v14 00/11] KVM: x86/pmu: Guest Last Branch Recording
 Enabling
To:     <like.xu.linux@gmail.com>, <alex.shi@linux.alibaba.com>,
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        Xiexiangyou <xiexiangyou@huawei.com>
From:   Liuxiangdong <liuxiangdong5@huawei.com>
Message-ID: <61036EEC.4020006@huawei.com>
Date:   Fri, 30 Jul 2021 11:15:56 +0800
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Hi, like.

Does it have requirement on CPU if we want to use LBR in Guest?

I have tried linux-5.14-rc3 on different CPUs. And I can use lbr on 
Haswell, Broadwell, skylake and icelake, but I cannot use lbr on IvyBridge.

Thanks!


On 2021/7/29 20:40, Liuxiangdong wrote:
> 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