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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id i4sm4671308eja.92.2020.05.28.04.39.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 May 2020 04:39:22 -0700 (PDT) From: Vitaly Kuznetsov To: Paolo Bonzini , kvm@vger.kernel.org, x86@kernel.org Cc: Andy Lutomirski , Thomas Gleixner , Borislav Petkov , "H. Peter Anvin" , Wanpeng Li , Sean Christopherson , Jim Mattson , Vivek Goyal , Gavin Shan , Peter Zijlstra , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 06/10] KVM: x86: acknowledgment mechanism for async pf page ready notifications In-Reply-To: References: <20200525144125.143875-1-vkuznets@redhat.com> <20200525144125.143875-7-vkuznets@redhat.com> Date: Thu, 28 May 2020 13:39:21 +0200 Message-ID: <87wo4w2sra.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Paolo Bonzini writes: > On 25/05/20 16:41, Vitaly Kuznetsov wrote: >> + case MSR_KVM_ASYNC_PF_ACK: >> + if (data & 0x1) { >> + vcpu->arch.apf.pageready_pending = false; >> + kvm_check_async_pf_completion(vcpu); >> + } >> + break; >> case MSR_KVM_STEAL_TIME: >> >> if (unlikely(!sched_info_on())) >> @@ -3183,6 +3189,9 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) >> case MSR_KVM_ASYNC_PF_INT: >> msr_info->data = vcpu->arch.apf.msr_int_val; >> break; >> + case MSR_KVM_ASYNC_PF_ACK: >> + msr_info->data = 0; >> + break; > > How is the pageready_pending flag migrated? Should we revert the > direction of the MSR (i.e. read the flag, and write 0 to clear it)? The flag is not migrated so it will be 'false'. This can just cause an extra kick in kvm_arch_async_page_present_queued() but this shouldn't be a big deal. Also, after migration we will just send 'wakeup all' event, async pf queue will be empty. MSR_KVM_ASYNC_PF_ACK by itself is not migrated, we don't even store it, not sure how invering it would change things. -- Vitaly