[6/6] Nested SVM: Improve interrupt injection

Commit Message

Alexander Graf May 15, 2009, 8:22 a.m. UTC

While trying to get Hyper-V running, I realized that the interrupt injection
mechanisms that are in place right now are not 100% correct.

This patch makes nested SVM's interrupt injection behave more like on a
real machine.

Signed-off-by: Alexander Graf <[e-mail]>
---
 arch/x86/kvm/svm.c |   40 +++++++++++++++++++++++++---------------
 1 files changed, 25 insertions(+), 15 deletions(-)

Comments

Gleb Natapov May 17, 2009, 6:48 a.m. UTC | #1

On Fri, May 15, 2009 at 10:22:20AM +0200, Alexander Graf wrote:
>  static void svm_set_irq(struct kvm_vcpu *vcpu, int irq)
>  {
>  	struct vcpu_svm *svm = to_svm(vcpu);
>  
> -	nested_svm_intr(svm);
> +	if(!(svm->vcpu.arch.hflags & HF_GIF_MASK))
> +		return;
>  
Why would this function be called if HF_GIF_MASK is not set? This
check is done in svm_interrupt_allowed().

> -	svm_queue_irq(vcpu, irq);
> +	svm->vmcb->control.event_inj = irq |
> +		SVM_EVTINJ_VALID | SVM_EVTINJ_TYPE_INTR;
>  }
>  

--
			Gleb.
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Alexander Graf May 17, 2009, 8:10 a.m. UTC | #2

On 17.05.2009, at 08:48, Gleb Natapov <[e-mail]> wrote:

> On Fri, May 15, 2009 at 10:22:20AM +0200, Alexander Graf wrote:
>> static void svm_set_irq(struct kvm_vcpu *vcpu, int irq)
>> {
>>    struct vcpu_svm *svm = to_svm(vcpu);
>>
>> -    nested_svm_intr(svm);
>> +    if(!(svm->vcpu.arch.hflags & HF_GIF_MASK))
>> +        return;
>>
> Why would this function be called if HF_GIF_MASK is not set? This
> check is done in svm_interrupt_allowed().

I agree it shouldn't but I don't remember why exactly it triggered  
here. I'll try and get a backtrace tomorrow.

Either way, if it's not a return, it's a BUG().

Alex

>
>
>> -    svm_queue_irq(vcpu, irq);
>> +    svm->vmcb->control.event_inj = irq |
>> +        SVM_EVTINJ_VALID | SVM_EVTINJ_TYPE_INTR;
>> }
>>
>
> --
>            Gleb.
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Alexander Graf May 18, 2009, 11:47 a.m. UTC | #3

On 17.05.2009, at 08:48, Gleb Natapov wrote:

> On Fri, May 15, 2009 at 10:22:20AM +0200, Alexander Graf wrote:
>> static void svm_set_irq(struct kvm_vcpu *vcpu, int irq)
>> {
>> 	struct vcpu_svm *svm = to_svm(vcpu);
>>
>> -	nested_svm_intr(svm);
>> +	if(!(svm->vcpu.arch.hflags & HF_GIF_MASK))
>> +		return;
>>
> Why would this function be called if HF_GIF_MASK is not set? This
> check is done in svm_interrupt_allowed().

Looks like I was doing something odd - WARN_ON doesn't trigger (which  
is reasonable).

I think I put the check in when I still had nested_svm_intr() before,  
because that would unset GIF.

Alex

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Patch

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index b2c6cf3..1d22d46 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1517,7 +1517,8 @@  static int nested_svm_vmexit_real(struct vcpu_svm *svm, void *arg1,
 	/* Kill any pending exceptions */
 	if (svm->vcpu.arch.exception.pending == true)
 		nsvm_printk("WARNING: Pending Exception\n");
-	svm->vcpu.arch.exception.pending = false;
+	kvm_clear_exception_queue(&svm->vcpu);
+	kvm_clear_interrupt_queue(&svm->vcpu);
 
 	/* Restore selected save entries */
 	svm->vmcb->save.es = hsave->save.es;
@@ -1585,7 +1586,8 @@  static int nested_svm_vmrun(struct vcpu_svm *svm, void *arg1,
 	svm->nested_vmcb = svm->vmcb->save.rax;
 
 	/* Clear internal status */
-	svm->vcpu.arch.exception.pending = false;
+	kvm_clear_exception_queue(&svm->vcpu);
+	kvm_clear_interrupt_queue(&svm->vcpu);
 
 	/* Save the old vmcb, so we don't need to pick what we save, but
 	   can restore everything when a VMEXIT occurs */
@@ -2276,21 +2278,15 @@  static inline void svm_inject_irq(struct vcpu_svm *svm, int irq)
 		((/*control->int_vector >> 4*/ 0xf) << V_INTR_PRIO_SHIFT);
 }
 
-static void svm_queue_irq(struct kvm_vcpu *vcpu, unsigned nr)
-{
-	struct vcpu_svm *svm = to_svm(vcpu);
-
-	svm->vmcb->control.event_inj = nr |
-		SVM_EVTINJ_VALID | SVM_EVTINJ_TYPE_INTR;
-}
-
 static void svm_set_irq(struct kvm_vcpu *vcpu, int irq)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 
-	nested_svm_intr(svm);
+	if(!(svm->vcpu.arch.hflags & HF_GIF_MASK))
+		return;
 
-	svm_queue_irq(vcpu, irq);
+	svm->vmcb->control.event_inj = irq |
+		SVM_EVTINJ_VALID | SVM_EVTINJ_TYPE_INTR;
 }
 
 static void update_cr8_intercept(struct kvm_vcpu *vcpu, int tpr, int irr)
@@ -2318,13 +2314,25 @@  static int svm_interrupt_allowed(struct kvm_vcpu *vcpu)
 	struct vmcb *vmcb = svm->vmcb;
 	return (vmcb->save.rflags & X86_EFLAGS_IF) &&
 		!(vmcb->control.int_state & SVM_INTERRUPT_SHADOW_MASK) &&
-		(svm->vcpu.arch.hflags & HF_GIF_MASK);
+		(svm->vcpu.arch.hflags & HF_GIF_MASK) &&
+		!is_nested(svm);
 }
 
 static void enable_irq_window(struct kvm_vcpu *vcpu)
 {
-	svm_set_vintr(to_svm(vcpu));
-	svm_inject_irq(to_svm(vcpu), 0x0);
+	struct vcpu_svm *svm = to_svm(vcpu);
+	nsvm_printk("Trying to open IRQ window\n");
+
+	nested_svm_intr(svm);
+
+	/* In case GIF=0 we can't rely on the CPU to tell us when
+	 * GIF becomes 1, because that's a separate STGI/VMRUN intercept.
+	 * The next time we get that intercept, this function will be
+	 * called again though and we'll get the vintr intercept. */
+	if (svm->vcpu.arch.hflags & HF_GIF_MASK) {
+		svm_set_vintr(svm);
+		svm_inject_irq(svm, 0x0);
+	}
 }
 
 static void enable_nmi_window(struct kvm_vcpu *vcpu)
@@ -2392,6 +2400,8 @@  static void svm_complete_interrupts(struct vcpu_svm *svm)
 	case SVM_EXITINTINFO_TYPE_EXEPT:
 		/* In case of software exception do not reinject an exception
 		   vector, but re-execute and instruction instead */
+		if (is_nested(svm))
+			break;
 		if (vector == BP_VECTOR || vector == OF_VECTOR)
 			break;
 		if (exitintinfo & SVM_EXITINTINFO_VALID_ERR) {