From f8ea7c6049d5d0766b84c8107583ed0094773d06 Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Tue, 13 Aug 2019 15:53:30 +0200 Subject: x86: kvm: svm: propagate errors from skip_emulated_instruction() On AMD, kvm_x86_ops->skip_emulated_instruction(vcpu) can, in theory, fail: in !nrips case we call kvm_emulate_instruction(EMULTYPE_SKIP). Currently, we only do printk(KERN_DEBUG) when this happens and this is not ideal. Propagate the error up the stack. On VMX, skip_emulated_instruction() doesn't fail, we have two call sites calling it explicitly: handle_exception_nmi() and handle_task_switch(), we can just ignore the result. On SVM, we also have two explicit call sites: svm_queue_exception() and it seems we don't need to do anything there as we check if RIP was advanced or not. In task_switch_interception(), however, we are better off not proceeding to kvm_task_switch() in case skip_emulated_instruction() failed. Suggested-by: Sean Christopherson Signed-off-by: Vitaly Kuznetsov Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm.c | 36 ++++++++++++++++++++---------------- 1 file changed, 20 insertions(+), 16 deletions(-) (limited to 'arch/x86/kvm/svm.c') diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 18190333bde9..1ff786d04993 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -768,7 +768,7 @@ static void svm_set_interrupt_shadow(struct kvm_vcpu *vcpu, int mask) } -static void skip_emulated_instruction(struct kvm_vcpu *vcpu) +static int skip_emulated_instruction(struct kvm_vcpu *vcpu) { struct vcpu_svm *svm = to_svm(vcpu); @@ -777,18 +777,17 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu) svm->next_rip = svm->vmcb->control.next_rip; } - if (!svm->next_rip) { - if (kvm_emulate_instruction(vcpu, EMULTYPE_SKIP) != - EMULATE_DONE) - printk(KERN_DEBUG "%s: NOP\n", __func__); - return; - } + if (!svm->next_rip) + return kvm_emulate_instruction(vcpu, EMULTYPE_SKIP); + 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); svm_set_interrupt_shadow(vcpu, 0); + + return EMULATE_DONE; } static void svm_queue_exception(struct kvm_vcpu *vcpu) @@ -819,7 +818,7 @@ static void svm_queue_exception(struct kvm_vcpu *vcpu) * raises a fault that is not intercepted. Still better than * failing in all cases. */ - skip_emulated_instruction(&svm->vcpu); + (void)skip_emulated_instruction(&svm->vcpu); rip = kvm_rip_read(&svm->vcpu); svm->int3_rip = rip + svm->vmcb->save.cs.base; svm->int3_injected = rip - old_rip; @@ -3896,20 +3895,25 @@ static int task_switch_interception(struct vcpu_svm *svm) if (reason != TASK_SWITCH_GATE || int_type == SVM_EXITINTINFO_TYPE_SOFT || (int_type == SVM_EXITINTINFO_TYPE_EXEPT && - (int_vec == OF_VECTOR || int_vec == BP_VECTOR))) - skip_emulated_instruction(&svm->vcpu); + (int_vec == OF_VECTOR || int_vec == BP_VECTOR))) { + if (skip_emulated_instruction(&svm->vcpu) != EMULATE_DONE) + goto fail; + } if (int_type != SVM_EXITINTINFO_TYPE_SOFT) int_vec = -1; if (kvm_task_switch(&svm->vcpu, tss_selector, int_vec, reason, - has_error_code, error_code) == EMULATE_FAIL) { - svm->vcpu.run->exit_reason = KVM_EXIT_INTERNAL_ERROR; - svm->vcpu.run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION; - svm->vcpu.run->internal.ndata = 0; - return 0; - } + has_error_code, error_code) == EMULATE_FAIL) + goto fail; + return 1; + +fail: + svm->vcpu.run->exit_reason = KVM_EXIT_INTERNAL_ERROR; + svm->vcpu.run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION; + svm->vcpu.run->internal.ndata = 0; + return 0; } static int cpuid_interception(struct vcpu_svm *svm) -- cgit v1.2.3