[PATCH 2/2] powerpc/kvm: Remove comment related to moving PMU code to perf subsystem

[Nicholas Piggin]

Excerpts from Kajol Jain's message of July 11, 2022 1:49 pm:
> Commit aabcaf6ae2a0 ("KVM: PPC: Book3S HV P9: Move host OS save/restore
> functions to  built-in") added a comment in switch_pmu_to_guest
> function, indicating possibility of moving PMU handling code
> to perf subsystem. But perf subsystem code compilation depends upon
> the enablement of CONFIG_PERF_EVENTS whereas, kvm code don't have
> any dependency on this config.
> Patch remove this comment as switch_pmu_to_guest functionality is
> needed even if perf subsystem is disabled.
> 
> Signed-off-by: Kajol Jain <kjain at linux.ibm.com>

Does the host PMU state need to be saved/restored if we don't have
PERF_EVENTS enabled? Guest yes, but host maybe could become a no-op?

Thanks,
Nick

> ---
>  arch/powerpc/kvm/book3s_hv_p9_perf.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/book3s_hv_p9_perf.c b/arch/powerpc/kvm/book3s_hv_p9_perf.c
> index da3135cab9ea..44d24cca3df1 100644
> --- a/arch/powerpc/kvm/book3s_hv_p9_perf.c
> +++ b/arch/powerpc/kvm/book3s_hv_p9_perf.c
> @@ -44,12 +44,6 @@ void switch_pmu_to_guest(struct kvm_vcpu *vcpu,
>  
>  	/* Save host */
>  	if (ppc_get_pmu_inuse()) {
> -		/*
> -		 * It might be better to put PMU handling (at least for the
> -		 * host) in the perf subsystem because it knows more about what
> -		 * is being used.
> -		 */
> -
>  		/* POWER9, POWER10 do not implement HPMC or SPMC */
>  
>  		host_os_sprs->mmcr0 = mfspr(SPRN_MMCR0);
> -- 
> 2.27.0
> 
>