arm/gicv3: Detect normal NC ITS command queues

GITS_CBASER.InnerCache uses the GIC BASER cacheability encoding.
Both 0b000 (Device-nGnRnE) and 0b001 (Normal Inner
Non-cacheable) describe non-cacheable accesses to the command queue.

its_map_cbaser() only checked whether the shifted field was zero,
so an ITS that reports Normal Inner Non-cacheable would not set
HOST_ITS_FLUSH_CMD_QUEUE. Decode the field before comparing it with
the unshifted enum value, matching the handling of ITS BASER tables
and GICR_PROPBASER.

Fixes: 8ed8d21373 ("ARM: GICv3 ITS: map ITS command buffer")
Signed-off-by: Mykola Kvach <mykola_kvach@epam.com>
Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/gic-v3-its.c

@@ -424,7 +424,8 @@ static void *its_map_cbaser(struct host_its *its)
      * If the command queue memory is mapped as uncached, we need to flush
      * it on every access.
      */
-    if ( !(reg & GITS_BASER_INNER_CACHEABILITY_MASK) )
+    if ( MASK_EXTR(reg, GITS_BASER_INNER_CACHEABILITY_MASK) <=
+         GIC_BASER_CACHE_nC )
     {
         its->flags |= HOST_ITS_FLUSH_CMD_QUEUE;
         printk(XENLOG_WARNING "using non-cacheable ITS command queue\n");