KVM: x86: WARN if the APIC map is dirty without an in-kernel local APIC

WARN if KVM ends up in a state where it thinks its APIC map needs to be
recalculated, but KVM is not emulating the local APIC.  This is mostly
to document KVM's "rules" in order to provide clarity in future cleanups.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210713163324.627647-12-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/lapic.c

@@ -192,6 +192,9 @@ void kvm_recalculate_apic_map(struct kvm *kvm)
 	if (atomic_read_acquire(&kvm->arch.apic_map_dirty) == CLEAN)
 		return;
 
+	WARN_ONCE(!irqchip_in_kernel(kvm),
+		  "Dirty APIC map without an in-kernel local APIC");
+
 	mutex_lock(&kvm->arch.apic_map_lock);
 	/*
 	 * Read kvm->arch.apic_map_dirty before kvm->arch.apic_map