xen/arm: Fix booting hwdom/1:1 domU with CONFIG_GRANT_TABLE=n

At the moment, we unconditionally allocate space for grant table region
membank and add it in the membanks array to find_unallocated_memory() to
find unused memory. In case of CONFIG_GRANT_TABLE=n, the size of the
region is empty and assertion in rangeset_remove_range() fails when
booting hwdom or 1:1 domU without IOMMU. Example:

(XEN) Assertion 's <= e' failed at common/rangeset.c:189
...
(XEN) Xen call trace:
(XEN)    [<00000a0000218b5c>] rangeset_remove_range+0xbc/0x2d4 (PC)
(XEN)    [<00000a00002b8370>] find_unallocated_memory+0x140/0x208 (LR)
(XEN)    [<00000a00002cc28c>] make_hypervisor_node+0x310/0x7e0
...

Same issue would occur when booting hwdom with LLC coloring enabled.
Fix it by performing conditional allocation and configuration.

Signed-off-by: Michal Orzel <michal.orzel@amd.com>
Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
Tested-by: Luca Fancellu <luca.fancellu@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/domain_build.c

@@ -1011,7 +1011,10 @@ static int __init find_host_extended_regions(const struct kernel_info *kinfo,
                                              struct membanks *ext_regions)
 {
     int res;
-    struct membanks *gnttab = membanks_xzalloc(1, MEMORY);
+    struct membanks *gnttab =
+        IS_ENABLED(CONFIG_GRANT_TABLE)
+        ? membanks_xzalloc(1, MEMORY)
+        : NULL;
     struct membanks *xen_reg =
         kinfo->xen_reg_assigned
         ? membanks_xzalloc(count_ranges(kinfo->xen_reg_assigned), MEMORY)
@@ -1037,12 +1040,6 @@ static int __init find_host_extended_regions(const struct kernel_info *kinfo,
 
     dt_dprintk("Find unallocated memory for extended regions\n");
 
-    if ( !gnttab )
-    {
-        res = -ENOMEM;
-        goto out;
-    }
-
     if ( kinfo->xen_reg_assigned )
     {
         if ( !xen_reg )
@@ -1056,9 +1053,17 @@ static int __init find_host_extended_regions(const struct kernel_info *kinfo,
                                rangeset_to_membank, xen_reg);
     }
 
+#ifdef CONFIG_GRANT_TABLE
+    if ( !gnttab )
+    {
+        res = -ENOMEM;
+        goto out;
+    }
+
     gnttab->nr_banks = 1;
     gnttab->bank[0].start = kinfo->gnttab_start;
     gnttab->bank[0].size = kinfo->gnttab_size;
+#endif
 
     res = find_unallocated_memory(kinfo, mem_banks, ARRAY_SIZE(mem_banks),
                                   ext_regions, add_ext_regions);

xen/common/device-tree/domain-build.c

@@ -250,7 +250,10 @@ void __init allocate_memory(struct domain *d, struct kernel_info *kinfo)
      */
     if ( is_hardware_domain(d) )
     {
-        struct membanks *gnttab = membanks_xzalloc(1, MEMORY);
+        struct membanks *gnttab =
+            IS_ENABLED(CONFIG_GRANT_TABLE)
+            ? membanks_xzalloc(1, MEMORY)
+            : NULL;
         /*
          * Exclude the following regions:
          * 1) Remove reserved memory
@@ -261,12 +264,14 @@ void __init allocate_memory(struct domain *d, struct kernel_info *kinfo)
             gnttab,
         };
 
+#ifdef CONFIG_GRANT_TABLE
         if ( !gnttab )
             goto fail;
 
         gnttab->nr_banks = 1;
         gnttab->bank[0].start = kinfo->gnttab_start;
         gnttab->bank[0].size = kinfo->gnttab_size;
+#endif
 
         hwdom_free_mem = membanks_xzalloc(NR_MEM_BANKS, MEMORY);
         if ( !hwdom_free_mem )