linux-kernel - Re: [RFC PATCH 06/41] perf: x86: Add function to switch PMI handler

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Message-ID: <Zhg3X_5A6BslIg-u@google.com>
Date: Thu, 11 Apr 2024 12:17:51 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Xiong Zhang <xiong.y.zhang@...ux.intel.com>
Cc: pbonzini@...hat.com, peterz@...radead.org, mizhang@...gle.com, 
	kan.liang@...el.com, zhenyuw@...ux.intel.com, dapeng1.mi@...ux.intel.com, 
	jmattson@...gle.com, kvm@...r.kernel.org, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org, zhiyuan.lv@...el.com, eranian@...gle.com, 
	irogers@...gle.com, samantha.alt@...el.com, like.xu.linux@...il.com, 
	chao.gao@...el.com, Xiong Zhang <xiong.y.zhang@...el.com>
Subject: Re: [RFC PATCH 06/41] perf: x86: Add function to switch PMI handler

On Fri, Jan 26, 2024, Xiong Zhang wrote:
> From: Xiong Zhang <xiong.y.zhang@...el.com>
> 
> Add function to switch PMI handler since passthrough PMU and host PMU will
> use different interrupt vectors.
> 
> Signed-off-by: Xiong Zhang <xiong.y.zhang@...el.com>
> Signed-off-by: Mingwei Zhang <mizhang@...gle.com>
> ---
>  arch/x86/events/core.c            | 15 +++++++++++++++
>  arch/x86/include/asm/perf_event.h |  3 +++
>  2 files changed, 18 insertions(+)
> 
> diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
> index 40ad1425ffa2..3f87894d8c8e 100644
> --- a/arch/x86/events/core.c
> +++ b/arch/x86/events/core.c
> @@ -701,6 +701,21 @@ struct perf_guest_switch_msr *perf_guest_get_msrs(int *nr, void *data)
>  }
>  EXPORT_SYMBOL_GPL(perf_guest_get_msrs);
>  
> +void perf_guest_switch_to_host_pmi_vector(void)
> +{
> +	lockdep_assert_irqs_disabled();
> +
> +	apic_write(APIC_LVTPC, APIC_DM_NMI);
> +}
> +EXPORT_SYMBOL_GPL(perf_guest_switch_to_host_pmi_vector);
> +
> +void perf_guest_switch_to_kvm_pmi_vector(void)
> +{
> +	lockdep_assert_irqs_disabled();
> +
> +	apic_write(APIC_LVTPC, APIC_DM_FIXED | KVM_VPMU_VECTOR);
> +}
> +EXPORT_SYMBOL_GPL(perf_guest_switch_to_kvm_pmi_vector);

Why slice and dice the context switch if it's all in perf?  Just do this in
perf_guest_enter().