Re: [PATCH v3 1/3] KVM: nVMX: Rework interception of IRQs and NMIs

[Paolo Bonzini <pbonzini@redhat.com>]

Il 07/03/2014 17:29, Jan Kiszka ha scritto:
> On 2014-03-07 16:44, Paolo Bonzini wrote:
>> With this patch do we still need
>>
>>         if (is_guest_mode(vcpu) && nested_exit_on_intr(vcpu))
>>                 /*
>>                  * We get here if vmx_interrupt_allowed() said we can't
>>                  * inject to L1 now because L2 must run. The caller will have
>>                  * to make L2 exit right after entry, so we can inject to L1
>>                  * more promptly.
>>                  */
>>                 return -EBUSY;
>>
>> in enable_irq_window?  If not, enable_nmi_window and enable_irq_window
>> can both return void.
> 
> I don't see right now why this should have changed. We still cannot
> interrupt vmlaunch/vmresume.

But then shouldn't the ame be true for enable_nmi_window?  It doesn't
check is_guest_mode(vcpu) && nested_exit_on_nmi(vcpu).

Since check_nested_events has already returned -EBUSY, perhaps the
following:

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index fda1028..df320e9 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4522,15 +4522,6 @@ static int enable_irq_window(struct kvm_vcpu *vcpu)
 {
 	u32 cpu_based_vm_exec_control;
 
-	if (is_guest_mode(vcpu) && nested_exit_on_intr(vcpu))
-		/*
-		 * We get here if vmx_interrupt_allowed() said we can't
-		 * inject to L1 now because L2 must run. The caller will have
-		 * to make L2 exit right after entry, so we can inject to L1
-		 * more promptly.
-		 */
-		return -EBUSY;
-
 	cpu_based_vm_exec_control = vmcs_read32(CPU_BASED_VM_EXEC_CONTROL);
 	cpu_based_vm_exec_control |= CPU_BASED_VIRTUAL_INTR_PENDING;
 	vmcs_write32(CPU_BASED_VM_EXEC_CONTROL, cpu_based_vm_exec_control);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a03d611..83c2df5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5970,13 +5970,13 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 
 		inject_pending_event(vcpu);
 
-		if (is_guest_mode(vcpu) && kvm_x86_ops->check_nested_events)
-			req_immediate_exit |=
-				kvm_x86_ops->check_nested_events(vcpu,
-							req_int_win) != 0;
+		if (is_guest_mode(vcpu) &&
+		    kvm_x86_ops->check_nested_events &&
+		    kvm_x86_ops->check_nested_events(vcpu, req_int_win) != 0)
+			req_immediate_exit = true;
 
 		/* enable NMI/IRQ window open exits if needed */
-		if (vcpu->arch.nmi_pending)
+		else if (vcpu->arch.nmi_pending)
 			req_immediate_exit |=
 				kvm_x86_ops->enable_nmi_window(vcpu) != 0;
                else if (kvm_cpu_has_injectable_intr(vcpu) || req_int_win)