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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id o2sm1258790wmh.46.2020.01.23.00.55.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Jan 2020 00:55:46 -0800 (PST) From: Vitaly Kuznetsov To: linmiaohe Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, pbonzini@redhat.com, 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 Subject: Re: [PATCH] KVM: nVMX: set rflags to specify success in handle_invvpid() default case In-Reply-To: <1579749241-712-1-git-send-email-linmiaohe@huawei.com> References: <1579749241-712-1-git-send-email-linmiaohe@huawei.com> Date: Thu, 23 Jan 2020 09:55:44 +0100 Message-ID: <8736c6sga7.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 linmiaohe writes: > From: Miaohe Lin > > In handle_invvpid() default case, we just skip emulated instruction and > forget to set rflags to specify success. This would result in indefinite > rflags value and thus indeterminate return value for guest. > > Signed-off-by: Miaohe Lin > --- > Chinese New Year is coming. Happy Spring Festival! ^_^ Happy Spring Festival! > --- > arch/x86/kvm/vmx/nested.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > 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? -- Vitaly