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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id q18sm19326723wmc.7.2021.10.25.08.57.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 25 Oct 2021 08:57:41 -0700 (PDT) Message-ID: Date: Mon, 25 Oct 2021 17:57:39 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.1.0 Subject: Re: [PATCH v2 37/43] KVM: SVM: Unconditionally mark AVIC as running on vCPU load (with APICv) Content-Language: en-US To: Sean Christopherson Cc: Marc Zyngier , Huacai Chen , Aleksandar Markovic , Paul Mackerras , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , James Morse , Alexandru Elisei , Suzuki K Poulose , Atish Patra , 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, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, David Matlack , Oliver Upton , Jing Zhang References: <20211009021236.4122790-1-seanjc@google.com> <20211009021236.4122790-38-seanjc@google.com> From: Paolo Bonzini In-Reply-To: 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 25/10/21 17:48, Sean Christopherson wrote: > On Mon, Oct 25, 2021, Paolo Bonzini wrote: >> On 09/10/21 04:12, Sean Christopherson wrote: >>> + /* TODO: Document why the unblocking path checks for updates. */ >> >> Is that a riddle or what? :) > > Yes? I haven't been able to figure out why the unblocking path explicitly > checks and handles an APICv update. > Challenge accepted. In the original code, it was because without it avic_vcpu_load would do nothing, and nothing would update the IS_RUNNING flag. It shouldn't be necessary anymore since commit df7e4827c549 ("KVM: SVM: call avic_vcpu_load/avic_vcpu_put when enabling/disabling AVIC", 2021-08-20), where svm_refresh_apicv_exec_ctrl takes care of the avic_vcpu_load on the next VMRUN. Paolo