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

Liuxiangdong
2021-07-29T12:40:15Z

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