irqchip/gic-v4.1: Implement the v4.1 flavour of VMAPP

The ITS VMAPP command gains some new fields with GICv4.1:
- a default doorbell, which allows a single doorbell to be used for
  all the VLPIs routed to a given VPE
- a pointer to the configuration table (instead of having it in a register
  that gets context switched)
- a flag indicating whether this is the first map or the last unmap for
  this particular VPE
- a flag indicating whether the pending table is known to be zeroed, or not

Plumb in the new fields in the VMAPP builder, and add the map/unmap
refcounting so that the ITS can do the right thing.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Link: https://lore.kernel.org/r/20191224111055.11836-7-maz@kernel.org

include/linux/irqchip/arm-gic-v4.h

@@ -39,8 +39,20 @@ struct its_vpe {
 	irq_hw_number_t		vpe_db_lpi;
 	/* VPE resident */
 	bool			resident;
-	/* VPE proxy mapping */
-	int			vpe_proxy_event;
+	union {
+		/* GICv4.0 implementations */
+		struct {
+			/* VPE proxy mapping */
+			int	vpe_proxy_event;
+			/* Implementation Defined Area Invalid */
+			bool	idai;
+		};
+		/* GICv4.1 implementations */
+		struct {
+			atomic_t vmapp_count;
+		};
+	};
+
 	/*
 	 * This collection ID is used to indirect the target
 	 * redistributor for this VPE. The ID itself isn't involved in
@@ -49,8 +61,6 @@ struct its_vpe {
 	u16			col_idx;
 	/* Unique (system-wide) VPE identifier */
 	u16			vpe_id;
-	/* Implementation Defined Area Invalid */
-	bool			idai;
 	/* Pending VLPIs on schedule out? */
 	bool			pending_last;
 };