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

Liuxiangdong
2021-07-30T03:16:16Z

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