| Message ID | 20190801051418.15905-4-vkuznets@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | x86: KVM: svm: get rid of hardcoded instructions lengths | expand |
On Thu, Aug 01, 2019 at 07:14:16AM +0200, Vitaly Kuznetsov wrote: > Regardless of the way how we skip instruction, interrupt shadow needs to be > cleared. > > Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> > Reviewed-by: Jim Mattson <jmattson@google.com> > --- > arch/x86/kvm/svm.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > index 80f576e05112..7c7dff3f461f 100644 > --- a/arch/x86/kvm/svm.c > +++ b/arch/x86/kvm/svm.c > @@ -784,13 +784,15 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu) > EMULATE_DONE) > pr_err_once("KVM: %s: unable to skip instruction\n", > __func__); > - return; > + goto clear_int_shadow; A better fix would be to clear the interrupt shadow in x86_emulate_instruction() after updating RIP for EMULTYPE_SKIP. VMX has this same flaw when running nested as handle_ept_misconfig() also expects the interrupt shadow to be handled by kvm_emulate_instruction(). Clearing the shadow if and only if the skipping is successful also means KVM isn't incorrectly zapping the shadow when emulation fails. diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 01e18caac825..f25521fb1c42 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6537,6 +6537,7 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, kvm_rip_write(vcpu, ctxt->_eip); if (ctxt->eflags & X86_EFLAGS_RF) kvm_set_rflags(vcpu, ctxt->eflags & ~X86_EFLAGS_RF); + kvm_x86_ops->set_interrupt_shadow(vcpu, 0); return EMULATE_DONE; } > } > if (svm->next_rip - kvm_rip_read(vcpu) > MAX_INST_SIZE) > printk(KERN_ERR "%s: ip 0x%lx next 0x%llx\n", > __func__, kvm_rip_read(vcpu), svm->next_rip); > > kvm_rip_write(vcpu, svm->next_rip); > + > +clear_int_shadow: > svm_set_interrupt_shadow(vcpu, 0); > } > > -- > 2.20.1 >
Sean Christopherson <sean.j.christopherson@intel.com> writes: > On Thu, Aug 01, 2019 at 07:14:16AM +0200, Vitaly Kuznetsov wrote: >> Regardless of the way how we skip instruction, interrupt shadow needs to be >> cleared. >> >> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> >> Reviewed-by: Jim Mattson <jmattson@google.com> >> --- >> arch/x86/kvm/svm.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c >> index 80f576e05112..7c7dff3f461f 100644 >> --- a/arch/x86/kvm/svm.c >> +++ b/arch/x86/kvm/svm.c >> @@ -784,13 +784,15 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu) >> EMULATE_DONE) >> pr_err_once("KVM: %s: unable to skip instruction\n", >> __func__); >> - return; >> + goto clear_int_shadow; > > A better fix would be to clear the interrupt shadow in x86_emulate_instruction() > after updating RIP for EMULTYPE_SKIP. VMX has this same flaw when running > nested as handle_ept_misconfig() also expects the interrupt shadow to be > handled by kvm_emulate_instruction(). Clearing the shadow if and only if > the skipping is successful also means KVM isn't incorrectly zapping the > shadow when emulation fails. Oh, nice catch actually! Will do in v2.
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 80f576e05112..7c7dff3f461f 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -784,13 +784,15 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu) EMULATE_DONE) pr_err_once("KVM: %s: unable to skip instruction\n", __func__); - return; + goto clear_int_shadow; } if (svm->next_rip - kvm_rip_read(vcpu) > MAX_INST_SIZE) printk(KERN_ERR "%s: ip 0x%lx next 0x%llx\n", __func__, kvm_rip_read(vcpu), svm->next_rip); kvm_rip_write(vcpu, svm->next_rip); + +clear_int_shadow: svm_set_interrupt_shadow(vcpu, 0); }