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[184.147.14.204]) by smtp.gmail.com with ESMTPSA id f24sm48984qka.5.2020.10.01.18.11.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Oct 2020 18:11:40 -0700 (PDT) Date: Thu, 1 Oct 2020 21:11:39 -0400 From: Peter Xu To: Alexander Graf Cc: kvm list , Aaron Lewis , Sean Christopherson , Paolo Bonzini , Jonathan Corbet , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , KarimAllah Raslan , Dan Carpenter , Maxim Levitsky , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v8 6/8] KVM: x86: VMX: Prevent MSR passthrough when MSR access is denied Message-ID: <20201002011139.GA5473@xz-x1> References: <20200925143422.21718-1-graf@amazon.com> <20200925143422.21718-7-graf@amazon.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200925143422.21718-7-graf@amazon.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, I reported in the v13 cover letter of kvm dirty ring series that this patch seems to have been broken. Today I tried to reproduce with a simplest vm, and after a closer look... On Fri, Sep 25, 2020 at 04:34:20PM +0200, Alexander Graf wrote: > @@ -3764,15 +3859,14 @@ static u8 vmx_msr_bitmap_mode(struct kvm_vcpu *vcpu) > return mode; > } > > -static void vmx_update_msr_bitmap_x2apic(struct kvm_vcpu *vcpu, > - unsigned long *msr_bitmap, u8 mode) > +static void vmx_update_msr_bitmap_x2apic(struct kvm_vcpu *vcpu, u8 mode) > { > int msr; > > - for (msr = 0x800; msr <= 0x8ff; msr += BITS_PER_LONG) { > - unsigned word = msr / BITS_PER_LONG; > - msr_bitmap[word] = (mode & MSR_BITMAP_MODE_X2APIC_APICV) ? 0 : ~0; > - msr_bitmap[word + (0x800 / sizeof(long))] = ~0; > + for (msr = 0x800; msr <= 0x8ff; msr++) { > + bool intercepted = !!(mode & MSR_BITMAP_MODE_X2APIC_APICV); > + > + vmx_set_intercept_for_msr(vcpu, msr, MSR_TYPE_RW, intercepted); > } > > if (mode & MSR_BITMAP_MODE_X2APIC) { ... I think we may want below change to be squashed: diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index d160aad59697..7d3f2815b04d 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -3781,9 +3781,10 @@ static void vmx_update_msr_bitmap_x2apic(struct kvm_vcpu *vcpu, u8 mode) int msr; for (msr = 0x800; msr <= 0x8ff; msr++) { - bool intercepted = !!(mode & MSR_BITMAP_MODE_X2APIC_APICV); + bool apicv = mode & MSR_BITMAP_MODE_X2APIC_APICV; - vmx_set_intercept_for_msr(vcpu, msr, MSR_TYPE_RW, intercepted); + vmx_set_intercept_for_msr(vcpu, msr, MSR_TYPE_R, !apicv); + vmx_set_intercept_for_msr(vcpu, msr, MSR_TYPE_W, true); } if (mode & MSR_BITMAP_MODE_X2APIC) { This fixes my problem the same as having this patch reverted. -- Peter Xu