KVM: arm/arm64: vgic: Add LPI translation cache definition

Add the basic data structure that expresses an MSI to LPI
translation as well as the allocation/release hooks.

The size of the cache is arbitrarily defined as 16*nr_vcpus.

Tested-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

include/kvm/arm_vgic.h

@@ -249,6 +249,9 @@ struct vgic_dist {
 	struct list_head	lpi_list_head;
 	int			lpi_list_count;
 
+	/* LPI translation cache */
+	struct list_head	lpi_translation_cache;
+
 	/* used by vgic-debug */
 	struct vgic_state_iter *iter;