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([2001:b07:6468:f312:b8fe:679e:87eb:c059]) by smtp.gmail.com with ESMTPSA id 16sm1874485wmi.0.2020.01.23.01.23.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 Jan 2020 01:23:44 -0800 (PST) Subject: Re: [PATCH] KVM: nVMX: set rflags to specify success in handle_invvpid() default case To: Vitaly Kuznetsov , linmiaohe Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, rkrcmar@redhat.com, sean.j.christopherson@intel.com, wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com References: <1579749241-712-1-git-send-email-linmiaohe@huawei.com> <8736c6sga7.fsf@vitty.brq.redhat.com> From: Paolo Bonzini Message-ID: <1a083ac8-3b01-fd2d-d867-2b3956cdef6d@redhat.com> Date: Thu, 23 Jan 2020 10:23:42 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <8736c6sga7.fsf@vitty.brq.redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 23/01/20 09:55, Vitaly Kuznetsov wrote: >> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c >> index 7608924ee8c1..985d3307ec56 100644 >> --- a/arch/x86/kvm/vmx/nested.c >> +++ b/arch/x86/kvm/vmx/nested.c >> @@ -5165,7 +5165,7 @@ static int handle_invvpid(struct kvm_vcpu *vcpu) >> break; >> default: >> WARN_ON_ONCE(1); >> - return kvm_skip_emulated_instruction(vcpu); >> + break; >> } >> >> return nested_vmx_succeed(vcpu); > Your patch seems to do the right thing, however, I started wondering if > WARN_ON_ONCE() is the right thing to do. SDM says that "If an > unsupported INVVPID type is specified, the instruction fails." and this > is similar to INVEPT and I decided to check what handle_invept() > does. Well, it does BUG_ON(). > > Are we doing the right thing in any of these cases? Yes, both INVEPT and INVVPID catch this earlier. For INVEPT: types = (vmx->nested.msrs.ept_caps >> VMX_EPT_EXTENT_SHIFT) & 6; if (type >= 32 || !(types & (1 << type))) return nested_vmx_failValid(vcpu, VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID); For INVVPID: types = (vmx->nested.msrs.vpid_caps & VMX_VPID_EXTENT_SUPPORTED_MASK) >> 8; if (type >= 32 || !(types & (1 << type))) return nested_vmx_failValid(vcpu, VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID); So I'm leaning towards not applying Miaohe's patch. Happy Mouse Year to everyone, here is an ASCII art (except for one Unicode character) mouse: __()() / o) ~~~~\_,__,_>° Thanks,