kvm: vmx: Handle VMLAUNCH/VMRESUME failure properly

On an early VMLAUNCH/VMRESUME failure (i.e. one which sets the
VM-instruction error field of the current VMCS), the launch state of
the current VMCS is not set to "launched," and the VM-exit information
fields of the current VMCS (including IDT-vectoring information and
exit reason) are stale.

On a late VMLAUNCH/VMRESUME failure (i.e. one which sets the high bit
of the exit reason field), the launch state of the current VMCS is not
set to "launched," and only two of the VM-exit information fields of
the current VMCS are modified (exit reason and exit
qualification). The remaining VM-exit information fields of the
current VMCS (including IDT-vectoring information, in particular) are
stale.
Signed-off-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx.c

@@ -9424,12 +9424,6 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
 				  | (1 << VCPU_EXREG_CR3));
 	vcpu->arch.regs_dirty = 0;
 
-	vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD);
-
-	vmx->loaded_vmcs->launched = 1;
-
-	vmx->exit_reason = vmcs_read32(VM_EXIT_REASON);
-
 	/*
 	 * eager fpu is enabled if PKEY is supported and CR4 is switched
 	 * back on host, so it is safe to read guest PKRU from current
@@ -9451,6 +9445,14 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
 		kvm_make_request(KVM_REQ_EVENT, vcpu);
 
 	vmx->nested.nested_run_pending = 0;
+	vmx->idt_vectoring_info = 0;
+
+	vmx->exit_reason = vmx->fail ? 0xdead : vmcs_read32(VM_EXIT_REASON);
+	if (vmx->fail || (vmx->exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY))
+		return;
+
+	vmx->loaded_vmcs->launched = 1;
+	vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD);
 
 	vmx_complete_atomic_exit(vmx);
 	vmx_recover_nmi_blocking(vmx);