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[PATCH 2/4] KVM: nVMX: fill nested IDT-vectored event info on all L2->L0 exits

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vcpu->arch.exception currently contains the vmcs02 IDT-vectored info
through the entire execution of the vmexit.  This makes it harder
to keep that information safe when vcpu->arch.exception is reused for
an exception that happens while L0 handles a vmexit.

When this happens, there are two cases:

- the exception causes a vmexit to L1; in that case, the exception in the
  IDT-vectored info is not reinjected; vcpu->arch.exception is
  reused to build the VM-exit interruption info.

- the exception doesn't cause a vmexit to L1; in that case,
  vcpu->arch.exception is changed to a double fault which is injected
  normally into L2 via KVM_REQ_EVENT.

We want to discard vcpu->arch.exception in the first case.  To prepare
for that, prepare the vmcs12 IDT-vectored info early.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/vmx.c | 127 +++++++++++++++++++++++++++++------------------------
 1 file changed, 69 insertions(+), 58 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 01c29b6af254..f8ef38094acc 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -9073,11 +9073,76 @@ static void __vmx_complete_interrupts(struct kvm_vcpu *vcpu,
 	}
 }
 
-static void vmx_complete_interrupts(struct vcpu_vmx *vmx)
+static void vmcs12_save_pending_event(struct kvm_vcpu *vcpu,
+				       struct vmcs12 *vmcs12)
+{
+	u32 idt_vectoring;
+	unsigned int nr;
+
+	if (vcpu->arch.exception.pending && vcpu->arch.exception.reinject) {
+		nr = vcpu->arch.exception.nr;
+		idt_vectoring = nr | VECTORING_INFO_VALID_MASK;
+
+		if (kvm_exception_is_soft(nr)) {
+			vmcs12->vm_exit_instruction_len =
+				vcpu->arch.event_exit_inst_len;
+			idt_vectoring |= INTR_TYPE_SOFT_EXCEPTION;
+		} else
+			idt_vectoring |= INTR_TYPE_HARD_EXCEPTION;
+
+		if (vcpu->arch.exception.has_error_code) {
+			idt_vectoring |= VECTORING_INFO_DELIVER_CODE_MASK;
+			vmcs12->idt_vectoring_error_code =
+				vcpu->arch.exception.error_code;
+		}
+
+		vmcs12->idt_vectoring_info_field = idt_vectoring;
+	} else if (vcpu->arch.nmi_injected) {
+		vmcs12->idt_vectoring_info_field =
+			INTR_TYPE_NMI_INTR | INTR_INFO_VALID_MASK | NMI_VECTOR;
+	} else if (vcpu->arch.interrupt.pending) {
+		nr = vcpu->arch.interrupt.nr;
+		idt_vectoring = nr | VECTORING_INFO_VALID_MASK;
+
+		if (vcpu->arch.interrupt.soft) {
+			idt_vectoring |= INTR_TYPE_SOFT_INTR;
+			vmcs12->vm_entry_instruction_len =
+				vcpu->arch.event_exit_inst_len;
+		} else
+			idt_vectoring |= INTR_TYPE_EXT_INTR;
+
+		vmcs12->idt_vectoring_info_field = idt_vectoring;
+	}
+}
+
+static void vmx_complete_interrupts(struct kvm_vcpu *vcpu)
 {
+	struct vcpu_vmx *vmx = to_vmx(vcpu);
+	struct vmcs12 *vmcs12;
+
 	__vmx_complete_interrupts(&vmx->vcpu, vmx->idt_vectoring_info,
 				  VM_EXIT_INSTRUCTION_LEN,
 				  IDT_VECTORING_ERROR_CODE);
+
+	if (!is_guest_mode(vcpu))
+		return;
+
+	/*
+	 * Nested vmexit during event delivery, move the IDT-vectored event
+	 * fields to _both_ vcpu->arch and VMCS12.  If we exit to L1, having it
+	 * in VMCS12 makes it easier to reuse vcpu->arch for a non-reinjected
+	 * exception and error code; if we stay in L2, the vmcs12 writes go
+	 * unnoticed.
+	 */
+
+	vmcs12 = get_vmcs12(vcpu);
+	vmcs12->idt_vectoring_info_field = 0;
+	vmcs12->vm_exit_instruction_len = vmcs_read32(VM_EXIT_INSTRUCTION_LEN);
+	vmcs12->vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
+
+	if ((vmx->idt_vectoring_info & VECTORING_INFO_VALID_MASK) &&
+	    !(vmcs12->vm_exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY))
+		vmcs12_save_pending_event(vcpu, vmcs12);
 }
 
 static void vmx_cancel_injection(struct kvm_vcpu *vcpu)
@@ -9343,7 +9408,7 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
 
 	vmx_complete_atomic_exit(vmx);
 	vmx_recover_nmi_blocking(vmx);
-	vmx_complete_interrupts(vmx);
+	vmx_complete_interrupts(vcpu);
 }
 STACK_FRAME_NON_STANDARD(vmx_vcpu_run);
 
@@ -10887,48 +10952,6 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 			vcpu->arch.cr4_guest_owned_bits));
 }
 
-static void vmcs12_save_pending_event(struct kvm_vcpu *vcpu,
-				       struct vmcs12 *vmcs12)
-{
-	u32 idt_vectoring;
-	unsigned int nr;
-
-	if (vcpu->arch.exception.pending && vcpu->arch.exception.reinject) {
-		nr = vcpu->arch.exception.nr;
-		idt_vectoring = nr | VECTORING_INFO_VALID_MASK;
-
-		if (kvm_exception_is_soft(nr)) {
-			vmcs12->vm_exit_instruction_len =
-				vcpu->arch.event_exit_inst_len;
-			idt_vectoring |= INTR_TYPE_SOFT_EXCEPTION;
-		} else
-			idt_vectoring |= INTR_TYPE_HARD_EXCEPTION;
-
-		if (vcpu->arch.exception.has_error_code) {
-			idt_vectoring |= VECTORING_INFO_DELIVER_CODE_MASK;
-			vmcs12->idt_vectoring_error_code =
-				vcpu->arch.exception.error_code;
-		}
-
-		vmcs12->idt_vectoring_info_field = idt_vectoring;
-	} else if (vcpu->arch.nmi_injected) {
-		vmcs12->idt_vectoring_info_field =
-			INTR_TYPE_NMI_INTR | INTR_INFO_VALID_MASK | NMI_VECTOR;
-	} else if (vcpu->arch.interrupt.pending) {
-		nr = vcpu->arch.interrupt.nr;
-		idt_vectoring = nr | VECTORING_INFO_VALID_MASK;
-
-		if (vcpu->arch.interrupt.soft) {
-			idt_vectoring |= INTR_TYPE_SOFT_INTR;
-			vmcs12->vm_entry_instruction_len =
-				vcpu->arch.event_exit_inst_len;
-		} else
-			idt_vectoring |= INTR_TYPE_EXT_INTR;
-
-		vmcs12->idt_vectoring_info_field = idt_vectoring;
-	}
-}
-
 static int vmx_check_nested_events(struct kvm_vcpu *vcpu, bool external_intr)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -11123,21 +11146,9 @@ static void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 	vmcs12->exit_qualification = exit_qualification;
 	vmcs12->vm_exit_intr_info = exit_intr_info;
 
-	vmcs12->idt_vectoring_info_field = 0;
-	vmcs12->vm_exit_instruction_len = vmcs_read32(VM_EXIT_INSTRUCTION_LEN);
-	vmcs12->vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
-
-	if (!(vmcs12->vm_exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY)) {
-		/*
-		 * Transfer the event that L0 or L1 may wanted to inject into
-		 * L2 to IDT_VECTORING_INFO_FIELD.
-		 */
-		vmcs12_save_pending_event(vcpu, vmcs12);
-	}
-
 	/*
-	 * Drop what we picked up for L2 via vmx_complete_interrupts. It is
-	 * preserved above and would only end up incorrectly in L1.
+	 * Clear these, they are already in vmcs12 via exit interruption info
+	 * or IDT-vectored event info.
 	 */
 	vcpu->arch.nmi_injected = false;
 	kvm_clear_exception_queue(vcpu);
-- 
1.8.3.1

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[RFC PATCH 0/4] KVM: x86: allow overwriting L2 reinjected exception with L1 vmexit Paolo Bonzini <pbonzini@redhat.com> - 2017-08-23 22:50 +0200
  [PATCH 3/4] KVM: x86: pass struct kvm_queued_exception to kvm_multiple_exception Paolo Bonzini <pbonzini@redhat.com> - 2017-08-23 22:50 +0200
  [PATCH 2/4] KVM: nVMX: fill nested IDT-vectored event info on all L2->L0 exits Paolo Bonzini <pbonzini@redhat.com> - 2017-08-23 22:50 +0200
  [PATCH 4/4] KVM: x86: allow overwriting L2 reinjected exception with L1 vmexit Paolo Bonzini <pbonzini@redhat.com> - 2017-08-23 22:50 +0200

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