Re: [PATCH] x86/perf: Fix guest_get_msrs static call if there is no PMU

[Xu, Like]

On 2021/3/8 16:53, Peter Zijlstra wrote:
> Still, it calling atomic_switch_perf_msrs() and
> intel_pmu_lbr_is_enabled() when there isn't a PMU at all is of course, a
> complete waste of cycles.

This suggestion is reminiscent of a sad regression of optimizing it:

https://lore.kernel.org/kvm/20200619094046.654019-1-vkuznets@xxxxxxxxxx/
https://lore.kernel.org/kvm/20210209225653.1393771-1-jmattson@xxxxxxxxxx/