[RFC PATCH v3 01/19] KVM: x86: document AVIC/APICv inhibit reasons

[Maxim Levitsky]

These days there are too many AVIC/APICv inhibit
reasons, and it doesn't hurt to have some documentation
for them.

Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
---
 arch/x86/include/asm/kvm_host.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f164c6c1514a4..63eae00625bda 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1046,14 +1046,29 @@ struct kvm_x86_msr_filter {
 };
 
 enum kvm_apicv_inhibit {
+	/* APICv/AVIC is disabled by module param and/or not supported in hardware */
 	APICV_INHIBIT_REASON_DISABLE,
+	/* APICv/AVIC is inhibited because AutoEOI feature is being used by a HyperV guest*/
 	APICV_INHIBIT_REASON_HYPERV,
+	/* AVIC is inhibited on a CPU because it runs a nested guest */
 	APICV_INHIBIT_REASON_NESTED,
+	/* AVIC is inhibited due to wait for an irq window (AVIC doesn't support this) */
 	APICV_INHIBIT_REASON_IRQWIN,
+	/*
+	 * AVIC is inhibited because i8254 're-inject' mode is used
+	 * which needs EOI intercept which AVIC doesn't support
+	 */
 	APICV_INHIBIT_REASON_PIT_REINJ,
+	/* AVIC is inhibited because the guest has x2apic in its CPUID*/
 	APICV_INHIBIT_REASON_X2APIC,
+	/* AVIC/APICv is inhibited because KVM_GUESTDBG_BLOCKIRQ was enabled */
 	APICV_INHIBIT_REASON_BLOCKIRQ,
+	/*
+	 * AVIC/APICv is inhibited because the guest didn't yet
+	 * enable kernel/split irqchip
+	 */
 	APICV_INHIBIT_REASON_ABSENT,
+	/* AVIC is disabled because SEV doesn't support it */
 	APICV_INHIBIT_REASON_SEV,
 };
 
-- 
2.26.3