irqchip/gic-v3-its: Honor hypervisor enforced LPI range

A recent extension to the GIC architecture allows a hypervisor to
arbitrarily reduce the number of LPIs available to a guest, no
matter what the GIC says about the valid range of IntIDs.

Let's factor in this information when computing the number of
available LPIs

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

drivers/irqchip/irq-gic-v3-its.c

@@ -1541,8 +1541,17 @@ out:
 static int __init its_lpi_init(u32 id_bits)
 {
 	u32 lpis = (1UL << id_bits) - 8192;
+	u32 numlpis;
 	int err;
 
+	numlpis = 1UL << GICD_TYPER_NUM_LPIS(gic_rdists->gicd_typer);
+
+	if (numlpis > 2 && !WARN_ON(numlpis > lpis)) {
+		lpis = numlpis;
+		pr_info("ITS: Using hypervisor restricted LPI range [%u]\n",
+			lpis);
+	}
+
 	/*
 	 * Initializing the allocator is just the same as freeing the
 	 * full range of LPIs.