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[35.185.214.157]) by smtp.gmail.com with ESMTPSA id h13-20020a056a00230d00b004f427ffd485sm26051672pfh.143.2022.04.07.11.02.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Apr 2022 11:02:39 -0700 (PDT) Date: Thu, 7 Apr 2022 18:02:36 +0000 From: Sean Christopherson To: Vitaly Kuznetsov Cc: kvm@vger.kernel.org, Paolo Bonzini , Wanpeng Li , Jim Mattson , Michael Kelley , Siddharth Chandrasekaran , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 01/31] KVM: x86: hyper-v: Resurrect dedicated KVM_REQ_HV_TLB_FLUSH flag Message-ID: References: <20220407155645.940890-1-vkuznets@redhat.com> <20220407155645.940890-2-vkuznets@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220407155645.940890-2-vkuznets@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 07, 2022, Vitaly Kuznetsov wrote: > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index e9647614dc8c..3c54f6804b7b 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -3341,7 +3341,12 @@ void kvm_service_local_tlb_flush_requests(struct kvm_vcpu *vcpu) > if (kvm_check_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu)) > kvm_vcpu_flush_tlb_current(vcpu); > > - if (kvm_check_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu)) > + if (kvm_check_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu)) { > + kvm_vcpu_flush_tlb_guest(vcpu); > + kvm_clear_request(KVM_REQ_HV_TLB_FLUSH, vcpu); > + } > + > + if (kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu)) > kvm_vcpu_flush_tlb_guest(vcpu); It'd be slightly more performant to do: if (kvm_check_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu)) { kvm_vcpu_flush_tlb_guest(vcpu); kvm_clear_request(KVM_REQ_HV_TLB_FLUSH, vcpu); } else if (kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu)) { kvm_hv_vcpu_flush_tlb(vcpu); } And then when the code becomes if (kvm_check_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu)) { kvm_vcpu_flush_tlb_guest(vcpu); if (kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu)) kvm_hv_vcpu_empty_flush_tlb(vcpu); } else if (kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu)) { kvm_hv_vcpu_flush_tlb(vcpu); } the elif will help unsuspecting readers see that the HV_TLB_FLUSH request is cleared by kvm_check_request() in the TLB_FLUSH_GUEST path. The elif could result in having to bail from VM-Entry if the request becomes pending after the check/clear inside TLB_FLUSH_GUEST, but that should be a very rare case. > } > EXPORT_SYMBOL_GPL(kvm_service_local_tlb_flush_requests); > -- > 2.35.1 >