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From: Mingwei Zhang <mizhang@google.com>
Date: Tue, 23 Apr 2024 09:50:47 -0700
Message-ID: <CAL715WK60PeB5kmStfKq9pFb4CMf6DL5hjM5kMXEe+5yE_e_gw@mail.gmail.com>
Subject: Re: [RFC PATCH 23/41] KVM: x86/pmu: Implement the save/restore of PMU
 state for Intel CPU
To: "Mi, Dapeng" <dapeng1.mi@linux.intel.com>
Cc: maobibo <maobibo@loongson.cn>, Sean Christopherson <seanjc@google.com>, 
	Xiong Zhang <xiong.y.zhang@linux.intel.com>, pbonzini@redhat.com, peterz@infradead.org, 
	kan.liang@intel.com, zhenyuw@linux.intel.com, jmattson@google.com, 
	kvm@vger.kernel.org, linux-perf-users@vger.kernel.org, 
	linux-kernel@vger.kernel.org, zhiyuan.lv@intel.com, eranian@google.com, 
	irogers@google.com, samantha.alt@intel.com, like.xu.linux@gmail.com, 
	chao.gao@intel.com
Content-Type: text/plain; charset="UTF-8"

> > Is there any event in the host still having PERF_EVENT_STATE_ACTIVE?
> > If so, hmm, it will reach perf_pmu_disable(event->pmu), which will
> > access the global ctrl MSR.
>
> I don't think there is any event with PERF_EVENT_STATE_ACTIVE state on
> host when guest owns the PMU HW resource.
>
> In current solution, VM would fail to create if there is any system-wide
> event without exclude_guest attribute. If VM is created successfully and
> when vm-entry happens, the helper perf_guest_enter() would put all host
> events with exclude_guest attribute into PERF_EVENT_STATE_INACTIVE state
> and block host to create system-wide events without exclude_guest attribute.
>

Yeah, that's perfect.

Thanks.
-Mingwei