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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id f17sm24125202wrj.28.2020.03.03.08.35.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Mar 2020 08:35:54 -0800 (PST) From: Vitaly Kuznetsov To: Paolo Bonzini , kvm@vger.kernel.org Cc: Jim Mattson , Sean Christopherson , Bandan Das , Oliver Upton , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] KVM: x86: clear stale x86_emulate_ctxt->intercept value In-Reply-To: <4f933f77-6924-249a-77c5-3c904e7c052b@redhat.com> References: <20200303143316.834912-1-vkuznets@redhat.com> <20200303143316.834912-2-vkuznets@redhat.com> <4f933f77-6924-249a-77c5-3c904e7c052b@redhat.com> Date: Tue, 03 Mar 2020 17:35:53 +0100 Message-ID: <87zhcxe6qe.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 Paolo Bonzini writes: > On 03/03/20 15:33, Vitaly Kuznetsov wrote: >> Commit c44b4c6ab80e ("KVM: emulate: clean up initializations in >> init_decode_cache") reduced the number of fields cleared by >> init_decode_cache() claiming that they are being cleared elsewhere, >> 'intercept', however, seems to be left uncleared in some cases. >> >> The issue I'm observing manifests itself as following: >> after commit 07721feee46b ("KVM: nVMX: Don't emulate instructions in guest >> mode") Hyper-V guests on KVM stopped booting with: >> >> kvm_nested_vmexit: rip fffff802987d6169 reason EPT_VIOLATION info1 181 >> info2 0 int_info 0 int_info_err 0 >> kvm_page_fault: address febd0000 error_code 181 >> kvm_emulate_insn: 0:fffff802987d6169: f3 a5 >> kvm_emulate_insn: 0:fffff802987d6169: f3 a5 FAIL >> kvm_inj_exception: #UD (0x0) > > Slightly rephrased: > > After commit 07721feee46b ("KVM: nVMX: Don't emulate instructions in guest > mode") Hyper-V guests on KVM stopped booting with: > > kvm_nested_vmexit: rip fffff802987d6169 reason EPT_VIOLATION info1 181 > info2 0 int_info 0 int_info_err 0 > kvm_page_fault: address febd0000 error_code 181 > kvm_emulate_insn: 0:fffff802987d6169: f3 a5 > kvm_emulate_insn: 0:fffff802987d6169: f3 a5 FAIL > kvm_inj_exception: #UD (0x0) > > "f3 a5" is a "rep movsw" instruction, which should not be intercepted > at all. Commit c44b4c6ab80e ("KVM: emulate: clean up initializations in > init_decode_cache") reduced the number of fields cleared by > init_decode_cache() claiming that they are being cleared elsewhere, > 'intercept', however, is left uncleared if the instruction does not have > any of the "slow path" flags (NotImpl, Stack, Op3264, Sse, Mmx, CheckPerm, > NearBranch, No16 and of course Intercept itself). Much better, thanks) Please let me know if you want me to resubmit. -- Vitaly