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([2001:b07:6468:f312:1c09:f536:3de6:228c]) by smtp.googlemail.com with ESMTPSA id bg16-20020a170906a05000b006f3c03f5871sm1884081ejb.108.2022.04.27.09.19.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 Apr 2022 09:19:02 -0700 (PDT) Message-ID: Date: Wed, 27 Apr 2022 18:18:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH MANUALSEL 5.4 1/2] x86/kvm: Preserve BSP MSR_KVM_POLL_CONTROL across suspend/resume Content-Language: en-US To: Sasha Levin , linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Wanpeng Li , Marcelo Tosatti , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, kvm@vger.kernel.org References: <20220427155438.19612-1-sashal@kernel.org> From: Paolo Bonzini In-Reply-To: <20220427155438.19612-1-sashal@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/27/22 17:54, Sasha Levin wrote: > From: Wanpeng Li > > [ Upstream commit 0361bdfddca20c8855ea3bdbbbc9c999912b10ff ] > > MSR_KVM_POLL_CONTROL is cleared on reset, thus reverting guests to > host-side polling after suspend/resume. Non-bootstrap CPUs are > restored correctly by the haltpoll driver because they are hot-unplugged > during suspend and hot-plugged during resume; however, the BSP > is not hotpluggable and remains in host-sde polling mode after > the guest resume. The makes the guest pay for the cost of vmexits > every time the guest enters idle. > > Fix it by recording BSP's haltpoll state and resuming it during guest > resume. > > Cc: Marcelo Tosatti > Signed-off-by: Wanpeng Li > Message-Id: <1650267752-46796-1-git-send-email-wanpengli@tencent.com> > Signed-off-by: Paolo Bonzini > Signed-off-by: Sasha Levin > --- > arch/x86/kernel/kvm.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c > index 408b51aba293..f582dda8dd34 100644 > --- a/arch/x86/kernel/kvm.c > +++ b/arch/x86/kernel/kvm.c > @@ -59,6 +59,7 @@ static DEFINE_PER_CPU_DECRYPTED(struct kvm_vcpu_pv_apf_data, apf_reason) __align > DEFINE_PER_CPU_DECRYPTED(struct kvm_steal_time, steal_time) __aligned(64) __visible; > static int has_steal_clock = 0; > > +static int has_guest_poll = 0; > /* > * No need for any "IO delay" on KVM > */ > @@ -584,14 +585,26 @@ static int kvm_cpu_down_prepare(unsigned int cpu) > > static int kvm_suspend(void) > { > + u64 val = 0; > + > kvm_guest_cpu_offline(false); > > +#ifdef CONFIG_ARCH_CPUIDLE_HALTPOLL > + if (kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL)) > + rdmsrl(MSR_KVM_POLL_CONTROL, val); > + has_guest_poll = !(val & 1); > +#endif > return 0; > } > > static void kvm_resume(void) > { > kvm_cpu_online(raw_smp_processor_id()); > + > +#ifdef CONFIG_ARCH_CPUIDLE_HALTPOLL > + if (kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL) && has_guest_poll) > + wrmsrl(MSR_KVM_POLL_CONTROL, 0); > +#endif > } > > static struct syscore_ops kvm_syscore_ops = { Acked-by: Paolo Bonzini