From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Lutomirski Subject: Re: [PATCH 08/14] kvm: x86: don't kill guest on unknown exit reason Date: Fri, 24 Oct 2014 10:57:52 -0700 Message-ID: <544A9320.6010102@amacapital.net> References: <1414163245-18555-1-git-send-email-pbonzini@redhat.com> <1414163245-18555-9-git-send-email-pbonzini@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: "Michael S. Tsirkin" , stable@vger.kernel.org To: Paolo Bonzini , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Return-path: In-Reply-To: <1414163245-18555-9-git-send-email-pbonzini@redhat.com> Sender: stable-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 10/24/2014 08:07 AM, Paolo Bonzini wrote: > From: "Michael S. Tsirkin" > > KVM_EXIT_UNKNOWN is a kvm bug, we don't really know whether it was > triggered by a priveledged application. Let's not kill the guest: WARN > and inject #UD instead. This scares me a bit. For guest CPL3, it's probably okay. For guest CPL0, on the other hand, #UD might not use IST (or a task switch on 32-bit guests), resulting in possible corruption if unprivileged code controls SP. Admittedly, there aren't that many contexts from which that should happen (on Linux, at least), but something like #DF (or even a triple fault) might be safer if the guest is at CPL0 when this happens. --Andy > > Cc: stable@vger.kernel.org > Signed-off-by: Michael S. Tsirkin > Signed-off-by: Paolo Bonzini > --- > arch/x86/kvm/svm.c | 6 +++--- > arch/x86/kvm/vmx.c | 6 +++--- > 2 files changed, 6 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > index 00bed2c5e948..7527cefc5a43 100644 > --- a/arch/x86/kvm/svm.c > +++ b/arch/x86/kvm/svm.c > @@ -3551,9 +3551,9 @@ static int handle_exit(struct kvm_vcpu *vcpu) > > if (exit_code >= ARRAY_SIZE(svm_exit_handlers) > || !svm_exit_handlers[exit_code]) { > - kvm_run->exit_reason = KVM_EXIT_UNKNOWN; > - kvm_run->hw.hardware_exit_reason = exit_code; > - return 0; > + WARN_ONCE(1, "vmx: unexpected exit reason 0x%x\n", exit_code); > + kvm_queue_exception(vcpu, UD_VECTOR); > + return 1; > } > > return svm_exit_handlers[exit_code](svm); > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index cf3cd079ec52..a8b76c4c95e2 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -7174,10 +7174,10 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu) > && kvm_vmx_exit_handlers[exit_reason]) > return kvm_vmx_exit_handlers[exit_reason](vcpu); > else { > - vcpu->run->exit_reason = KVM_EXIT_UNKNOWN; > - vcpu->run->hw.hardware_exit_reason = exit_reason; > + WARN_ONCE(1, "vmx: unexpected exit reason 0x%x\n", exit_reason); > + kvm_queue_exception(vcpu, UD_VECTOR); > + return 1; > } > - return 0; > } > > static void update_cr8_intercept(struct kvm_vcpu *vcpu, int tpr, int irr) >