kvm: x86: lapic: remove one redundant judging condition

Finally we always return highest_irr so its unnecessary to return -1 after check if highest_irr == -1.

Signed-off-by Tiejun Chen <[email protected]>

---
 arch/x86/kvm/lapic.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

arch/x86/kvm/lapic.c +0 -0

index 5f574b4..e6a7eb6 100644

Quoted 13 lines · Tiejun Chen

Finally we always return highest_irr so its unnecessary to return -1 after check if highest_irr == -1.

Signed-off-by Tiejun Chen <[email protected]>

---
  arch/x86/kvm/lapic.c | 3 +--
  1 file changed, 1 insertion(+), 2 deletions(-)

arch/x86/kvm/lapic.c +0 -0

index 5f574b4..e6a7eb6 100644

arch/x86/kvm/lapic.c int kvm_apic_has_interrupt(struct kvm_vcpu *vcpu) · line 1644

Quoted 9 lines

arch/x86/kvm/lapic.c +1 -2

@@ -1638,8 +1638,7 @@ int kvm_apic_has_interrupt(struct kvm_vcpu *vcpu)
 
  	apic_update_ppr(apic);
  	highest_irr = apic_find_highest_irr(apic);
-	if ((highest_irr == -1) ||
-	    ((highest_irr & 0xF0) <= kvm_apic_get_reg(apic, APIC_PROCPRI)))
+	if ((highest_irr & 0xF0) <= kvm_apic_get_reg(apic, APIC_PROCPRI))
  		return -1;
  	return highest_irr;
  }

I think the code is clearer without this change.

The two returns mean:

- return -1: no interrupt to inject

- return highest_irr: inject this interrupt

With IRR equal to all zeroes (highest_irr = -1), your patch would make the "if" always false ("current PPR is low, can inject the interrupt"), but computing highest_irr & 0xF0 would make no sense if highest_irr == -1.

To put it another way, imagine the code looked like this:

static inline int int_prio(int vector)

{
	WARN_ON(vector == -1);
	return vector & 0xF0;
}

...

apic_update_ppr(apic);

  	highest_irr = apic_find_highest_irr(apic);
	if (highest_irr == -1 ||
	    int_prio(highest_irr) <= kvm_apic_get_reg(apic, APIC_PROCPRI))

return -1;
return highest_irr;

Then removing the check on highest_irr == -1 would trigger a warning.

Paolo