xen/arm: check max_init_domid validity

Before trying to create a dom0less guest, check that max_init_domid
increment will generate a valid domain ID, lower than
DOMID_FIRST_RESERVED.

Signed-off-by: Bertrand Marquis <bertrand.marquis@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/domain_build.c

@@ -3879,6 +3879,9 @@ void __init create_domUs(void)
         if ( !dt_device_is_compatible(node, "xen,domain") )
             continue;
 
+        if ( (max_init_domid + 1) >= DOMID_FIRST_RESERVED )
+            panic("No more domain IDs available\n");
+
         if ( dt_find_property(node, "xen,static-mem", NULL) )
             flags |= CDF_staticmem;