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/include/asm/kvm_host.h | 2 +- arch/x86/kvm/svm.c | 36 ++++++++++++++++++++---------------- arch/x86/kvm/vmx/vmx.c | 16 +++++++++++++--- arch/x86/kvm/x86.c | 6 ++++-- 4 files changed, 38 insertions(+), 22 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 74e88e5edd9c..707ae7ff8e1e 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1070,7 +1070,7 @@ struct kvm_x86_ops { void (*run)(struct kvm_vcpu *vcpu); int (*handle_exit)(struct kvm_vcpu *vcpu); - void (*skip_emulated_instruction)(struct kvm_vcpu *vcpu); + int (*skip_emulated_instruction)(struct kvm_vcpu *vcpu); void (*set_interrupt_shadow)(struct kvm_vcpu *vcpu, int mask); u32 (*get_interrupt_shadow)(struct kvm_vcpu *vcpu); void (*patch_hypercall)(struct kvm_vcpu *vcpu, 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) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 42ed3faa6af8..26cf4fe2ff5c 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -1472,8 +1472,11 @@ static int vmx_rtit_ctl_check(struct kvm_vcpu *vcpu, u64 data) return 0; } - -static void skip_emulated_instruction(struct kvm_vcpu *vcpu) +/* + * Returns an int to be compatible with SVM implementation (which can fail). + * Do not use directly, use skip_emulated_instruction() instead. + */ +static int __skip_emulated_instruction(struct kvm_vcpu *vcpu) { unsigned long rip; @@ -1483,6 +1486,13 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu) /* skipping an emulated instruction also counts */ vmx_set_interrupt_shadow(vcpu, 0); + + return EMULATE_DONE; +} + +static inline void skip_emulated_instruction(struct kvm_vcpu *vcpu) +{ + (void)__skip_emulated_instruction(vcpu); } static void vmx_clear_hlt(struct kvm_vcpu *vcpu) @@ -7705,7 +7715,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = { .run = vmx_vcpu_run, .handle_exit = vmx_handle_exit, - .skip_emulated_instruction = skip_emulated_instruction, + .skip_emulated_instruction = __skip_emulated_instruction, .set_interrupt_shadow = vmx_set_interrupt_shadow, .get_interrupt_shadow = vmx_get_interrupt_shadow, .patch_hypercall = vmx_patch_hypercall, diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 6b81c7609d09..73825abb92b3 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6390,9 +6390,11 @@ static void kvm_vcpu_do_singlestep(struct kvm_vcpu *vcpu, int *r) int kvm_skip_emulated_instruction(struct kvm_vcpu *vcpu) { unsigned long rflags = kvm_x86_ops->get_rflags(vcpu); - int r = EMULATE_DONE; + int r; - kvm_x86_ops->skip_emulated_instruction(vcpu); + r = kvm_x86_ops->skip_emulated_instruction(vcpu); + if (unlikely(r != EMULATE_DONE)) + return 0; /* * rflags is the old, "raw" value of the flags. The new value has -- cgit v1.2.3