[PATCH RFC] kvm: ignore apic polarity

["Michael S. Tsirkin" <mst@redhat.com>]

apic polarity in KVM does not work: too many things assume active high.
Let's not pretend it works, let's just ignore polarity flag.  If we ever
want to emulate it exactly, this will need a feature flag anyway.

Also report this to userspace: this makes it
possible to report the interrupt active-low
in ACPI, this way we are closer to real hardware.

This patch fixes OSX running on KVM.

Reported-by: "Gabriel L. Somlo" <gsomlo@gmail.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

---

Gabriel, could you confirm this fixes OSX for you?
If you can play with linux tweaking interrupt
to active low, that would be very nice too:
it's weekend here.

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 902f124..db29b27 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -674,6 +676,7 @@ struct kvm_ppc_smmu_info {
 #define KVM_CAP_ARM_EL1_32BIT 93
 #define KVM_CAP_SPAPR_MULTITCE 94
 #define KVM_CAP_EXT_EMUL_CPUID 95
+#define KVM_CAP_X86_IOAPIC_POLARITY_IGNORED 96
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index 2d68297..ad170b4 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -328,7 +328,6 @@ int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int irq_source_id,
 	irq_level = __kvm_irq_line_state(&ioapic->irq_states[irq],
 					 irq_source_id, level);
 	entry = ioapic->redirtbl[irq];
-	irq_level ^= entry.fields.polarity;
 	if (!irq_level) {
 		ioapic->irr &= ~mask;
 		ret = 1;