irqchip/gic-v3: Add GICv4.1 VPEID size discovery

While GICv4.0 mandates 16 bit worth of VPEIDs, GICv4.1 allows smaller
implementations to be built. Add the required glue to dynamically
compute the limit.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Link: https://lore.kernel.org/r/20191224111055.11836-3-maz@kernel.org
diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index b704214..6b0a8d6 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -121,7 +121,16 @@ struct its_node {
 #define ITS_ITT_ALIGN		SZ_256
 
 /* The maximum number of VPEID bits supported by VLPI commands */
-#define ITS_MAX_VPEID_BITS	(16)
+#define ITS_MAX_VPEID_BITS						\
+	({								\
+		int nvpeid = 16;					\
+		if (gic_rdists->has_rvpeid &&				\
+		    gic_rdists->gicd_typer2 & GICD_TYPER2_VIL)		\
+			nvpeid = 1 + (gic_rdists->gicd_typer2 &		\
+				      GICD_TYPER2_VID);			\
+									\
+		nvpeid;							\
+	})
 #define ITS_MAX_VPEID		(1 << (ITS_MAX_VPEID_BITS))
 
 /* Convert page order to size in bytes */