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[34.82.80.254]) by smtp.gmail.com with ESMTPSA id d7sm142548pfq.43.2021.09.28.15.14.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Sep 2021 15:14:57 -0700 (PDT) Date: Tue, 28 Sep 2021 22:14:54 +0000 From: David Matlack To: Sean Christopherson Cc: Marc Zyngier , Huacai Chen , Aleksandar Markovic , Paul Mackerras , Christian Borntraeger , Janosch Frank , Paolo Bonzini , James Morse , Alexandru Elisei , Suzuki K Poulose , David Hildenbrand , Cornelia Huck , Claudio Imbrenda , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, linux-kernel@vger.kernel.org, Jing Zhang Subject: Re: [PATCH 14/14] KVM: x86: Invoke kvm_vcpu_block() directly for non-HALTED wait states Message-ID: References: <20210925005528.1145584-1-seanjc@google.com> <20210925005528.1145584-15-seanjc@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210925005528.1145584-15-seanjc@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On Fri, Sep 24, 2021 at 05:55:28PM -0700, Sean Christopherson wrote: > Call kvm_vcpu_block() directly for all wait states except HALTED so that > kvm_vcpu_halt() is no longer a misnomer on x86. > > Functionally, this means KVM will never attempt halt-polling or adjust > vcpu->halt_poll_ns for INIT_RECEIVED (a.k.a. Wait-For-SIPI (WFS)) or > AP_RESET_HOLD; UNINITIALIZED is handled in kvm_arch_vcpu_ioctl_run(), > and x86 doesn't use any other "wait" states. > > As mentioned above, the motivation of this is purely so that "halt" isn't > overloaded on x86, e.g. in KVM's stats. Skipping halt-polling for WFS > (and RESET_HOLD) has no meaningful effect on guest performance as there > are typically single-digit numbers of INIT-SIPI sequences per AP vCPU, > per boot, versus thousands of HLTs just to boot to console. > > Signed-off-by: Sean Christopherson Reviewed-by: David Matlack > --- > arch/x86/kvm/x86.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index b444f9315766..a0f313c4bc49 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -9893,7 +9893,10 @@ static inline int vcpu_block(struct kvm *kvm, struct kvm_vcpu *vcpu) > if (!kvm_arch_vcpu_runnable(vcpu) && > (!kvm_x86_ops.pre_block || static_call(kvm_x86_pre_block)(vcpu) == 0)) { > srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx); > - kvm_vcpu_halt(vcpu); > + if (vcpu->arch.mp_state == KVM_MP_STATE_HALTED) > + kvm_vcpu_halt(vcpu); > + else > + kvm_vcpu_block(vcpu); > vcpu->srcu_idx = srcu_read_lock(&kvm->srcu); > > if (kvm_x86_ops.post_block) > -- > 2.33.0.685.g46640cef36-goog >