From da998b46d244767505e41d050dcac5e4d03ba96f Mon Sep 17 00:00:00 2001 From: Jim Mattson Date: Tue, 16 Oct 2018 14:29:22 -0700 Subject: kvm: x86: Defer setting of CR2 until #PF delivery When exception payloads are enabled by userspace (which is not yet possible) and a #PF is raised in L2, defer the setting of CR2 until the #PF is delivered. This allows the L1 hypervisor to intercept the fault before CR2 is modified. For backwards compatibility, when exception payloads are not enabled by userspace, kvm_multiple_exception modifies CR2 when the #PF exception is raised. Reported-by: Jim Mattson Suggested-by: Paolo Bonzini Signed-off-by: Jim Mattson Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm.c | 13 ++++++------- arch/x86/kvm/vmx.c | 19 +++++++++---------- arch/x86/kvm/x86.c | 49 +++++++++++++++++++++++++++++++++++++++++++++---- arch/x86/kvm/x86.h | 2 ++ 4 files changed, 62 insertions(+), 21 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 47b07211c5b1..1086bebaeea3 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -805,6 +805,8 @@ static void svm_queue_exception(struct kvm_vcpu *vcpu) nested_svm_check_exception(svm, nr, has_error_code, error_code)) return; + kvm_deliver_exception_payload(&svm->vcpu); + if (nr == BP_VECTOR && !static_cpu_has(X86_FEATURE_NRIPS)) { unsigned long rip, old_rip = kvm_rip_read(&svm->vcpu); @@ -2965,16 +2967,13 @@ static int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr, svm->vmcb->control.exit_info_1 = error_code; /* - * FIXME: we should not write CR2 when L1 intercepts an L2 #PF exception. - * The fix is to add the ancillary datum (CR2 or DR6) to structs - * kvm_queued_exception and kvm_vcpu_events, so that CR2 and DR6 can be - * written only when inject_pending_event runs (DR6 would written here - * too). This should be conditional on a new capability---if the - * capability is disabled, kvm_multiple_exception would write the - * ancillary information to CR2 or DR6, for backwards ABI-compatibility. + * EXITINFO2 is undefined for all exception intercepts other + * than #PF. */ if (svm->vcpu.arch.exception.nested_apf) svm->vmcb->control.exit_info_2 = svm->vcpu.arch.apf.nested_apf_token; + else if (svm->vcpu.arch.exception.has_payload) + svm->vmcb->control.exit_info_2 = svm->vcpu.arch.exception.payload; else svm->vmcb->control.exit_info_2 = svm->vcpu.arch.cr2; diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 8d7c60faaacd..0c7efb1de29d 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -3292,27 +3292,24 @@ static int nested_vmx_check_exception(struct kvm_vcpu *vcpu, unsigned long *exit { struct vmcs12 *vmcs12 = get_vmcs12(vcpu); unsigned int nr = vcpu->arch.exception.nr; + bool has_payload = vcpu->arch.exception.has_payload; + unsigned long payload = vcpu->arch.exception.payload; if (nr == PF_VECTOR) { if (vcpu->arch.exception.nested_apf) { *exit_qual = vcpu->arch.apf.nested_apf_token; return 1; } - /* - * FIXME: we must not write CR2 when L1 intercepts an L2 #PF exception. - * The fix is to add the ancillary datum (CR2 or DR6) to structs - * kvm_queued_exception and kvm_vcpu_events, so that CR2 and DR6 - * can be written only when inject_pending_event runs. This should be - * conditional on a new capability---if the capability is disabled, - * kvm_multiple_exception would write the ancillary information to - * CR2 or DR6, for backwards ABI-compatibility. - */ if (nested_vmx_is_page_fault_vmexit(vmcs12, vcpu->arch.exception.error_code)) { - *exit_qual = vcpu->arch.cr2; + *exit_qual = has_payload ? payload : vcpu->arch.cr2; return 1; } } else { + /* + * FIXME: we must not write DR6 when L1 intercepts an + * L2 #DB exception. + */ if (vmcs12->exception_bitmap & (1u << nr)) { if (nr == DB_VECTOR) { *exit_qual = vcpu->arch.dr6; @@ -3349,6 +3346,8 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu) u32 error_code = vcpu->arch.exception.error_code; u32 intr_info = nr | INTR_INFO_VALID_MASK; + kvm_deliver_exception_payload(vcpu); + if (has_error_code) { vmcs_write32(VM_ENTRY_EXCEPTION_ERROR_CODE, error_code); intr_info |= INTR_INFO_DELIVER_CODE_MASK; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 25a2bac920bb..4e9536c335d6 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -400,6 +400,26 @@ static int exception_type(int vector) return EXCPT_FAULT; } +void kvm_deliver_exception_payload(struct kvm_vcpu *vcpu) +{ + unsigned nr = vcpu->arch.exception.nr; + bool has_payload = vcpu->arch.exception.has_payload; + unsigned long payload = vcpu->arch.exception.payload; + + if (!has_payload) + return; + + switch (nr) { + case PF_VECTOR: + vcpu->arch.cr2 = payload; + break; + } + + vcpu->arch.exception.has_payload = false; + vcpu->arch.exception.payload = 0; +} +EXPORT_SYMBOL_GPL(kvm_deliver_exception_payload); + static void kvm_multiple_exception(struct kvm_vcpu *vcpu, unsigned nr, bool has_error, u32 error_code, bool has_payload, unsigned long payload, bool reinject) @@ -441,6 +461,18 @@ static void kvm_multiple_exception(struct kvm_vcpu *vcpu, vcpu->arch.exception.error_code = error_code; vcpu->arch.exception.has_payload = has_payload; vcpu->arch.exception.payload = payload; + /* + * In guest mode, payload delivery should be deferred, + * so that the L1 hypervisor can intercept #PF before + * CR2 is modified. However, for ABI compatibility + * with KVM_GET_VCPU_EVENTS and KVM_SET_VCPU_EVENTS, + * we can't delay payload delivery unless userspace + * has enabled this functionality via the per-VM + * capability, KVM_CAP_EXCEPTION_PAYLOAD. + */ + if (!vcpu->kvm->arch.exception_payload_enabled || + !is_guest_mode(vcpu)) + kvm_deliver_exception_payload(vcpu); return; } @@ -486,6 +518,13 @@ void kvm_requeue_exception(struct kvm_vcpu *vcpu, unsigned nr) } EXPORT_SYMBOL_GPL(kvm_requeue_exception); +static void kvm_queue_exception_e_p(struct kvm_vcpu *vcpu, unsigned nr, + u32 error_code, unsigned long payload) +{ + kvm_multiple_exception(vcpu, nr, true, error_code, + true, payload, false); +} + int kvm_complete_insn_gp(struct kvm_vcpu *vcpu, int err) { if (err) @@ -502,11 +541,13 @@ void kvm_inject_page_fault(struct kvm_vcpu *vcpu, struct x86_exception *fault) ++vcpu->stat.pf_guest; vcpu->arch.exception.nested_apf = is_guest_mode(vcpu) && fault->async_page_fault; - if (vcpu->arch.exception.nested_apf) + if (vcpu->arch.exception.nested_apf) { vcpu->arch.apf.nested_apf_token = fault->address; - else - vcpu->arch.cr2 = fault->address; - kvm_queue_exception_e(vcpu, PF_VECTOR, fault->error_code); + kvm_queue_exception_e(vcpu, PF_VECTOR, fault->error_code); + } else { + kvm_queue_exception_e_p(vcpu, PF_VECTOR, fault->error_code, + fault->address); + } } EXPORT_SYMBOL_GPL(kvm_inject_page_fault); diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h index 67b9568613f3..224cd0a47568 100644 --- a/arch/x86/kvm/x86.h +++ b/arch/x86/kvm/x86.h @@ -266,6 +266,8 @@ int kvm_write_guest_virt_system(struct kvm_vcpu *vcpu, int handle_ud(struct kvm_vcpu *vcpu); +void kvm_deliver_exception_payload(struct kvm_vcpu *vcpu); + void kvm_vcpu_mtrr_init(struct kvm_vcpu *vcpu); u8 kvm_mtrr_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn); bool kvm_mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data); -- cgit v1.2.3-59-g8ed1b