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

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Il 07/03/2014 19:19, Jan Kiszka ha scritto:
On 2014-03-07 18:28, Jan Kiszka wrote:
On 2014-03-07 17:46, Paolo Bonzini wrote:
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).

Yes, that seems wrong now. But I need to think this through again, why
we may have excluded NMIs from this test so far.


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)


Hmm, looks reasonable.

Also on second thought. I can give this hunk some test cycles here, just
in case.

Thanks.

Reading through my code again, I'm now wondering why I added
check_nested_events to both inject_pending_event and vcpu_enter_guest.
The former seems redundant, only vcpu_enter_guest calls
inject_pending_event. I guess I forgot a cleanup here.

I can fold in your changes when I resend for the other cleanup.

As you prefer, I can also post it as a separate patch (my changes above do not have the int->void change).

I had pushed your patches already to kvm/queue. You can post v4 relative to kvm/next.

Paolo

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