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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id o14sm8403568edw.36.2021.06.23.05.30.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 23 Jun 2021 05:30:38 -0700 (PDT) Subject: Re: [PATCH] KVM: nVMX: Handle split-lock #AC exceptions that happen in L2 To: Xiaoyao Li , Sean Christopherson Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210622172244.3561540-1-seanjc@google.com> <5196d26a-abb5-7ec9-70b1-69912a45ecd7@intel.com> From: Paolo Bonzini Message-ID: Date: Wed, 23 Jun 2021 14:30:37 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <5196d26a-abb5-7ec9-70b1-69912a45ecd7@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 23/06/21 04:43, Xiaoyao Li wrote: >> >> +        else if (is_alignment_check(intr_info) && >> +             !vmx_guest_inject_ac(vcpu)) >> +            return true; > > Why choose to check in nested_vmx_l0_wants_exit, not in > nested_vmx_l1_wants_exit()? nested_vmx_l0_wants_exit() == true means "this is a vmexit that needs some transformation before being injected into L1". Instead, nested_vmx_l1_wants_exit() == true means "this is an event that should either be processed directly by L0, or cause a vmexit in L1" Typically, nested_vmx_l1_wants_exit() checks the controls in vmcs12, while nested_vmx_l0_wants_exit() returns true unconditionally for most vmexits; for others it checks processor state, or other state set up by userspace with ioctls such as vcpu->guest_debug. In this case it's *L0* that wants that vmexit, in order to either disable split-lock detection or inject a SIGBUS, so nested_vmx_l0_wants_exit() is the right one to test. Paolo