[PATCH for-4.16] xen/arm: don't assign domU static-mem to dom0 as reserved-memory

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>

DomUs static-mem ranges are added to the reserved_mem array for
accounting, but they shouldn't be assigned to dom0 as the other regular
reserved-memory ranges in device tree.

In make_memory_nodes, fix the error by skipping banks with xen_domain
set to true in the reserved-memory array. Also make sure to use the
first valid (!xen_domain) start address for the memory node name.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
---

This patch should be considered for 4.16 as it fixes an incorrect
behavior.

The risk is low for two reasons:
- the change is simple
- make_memory_node is easily tested because it gets called at every
  boot, e.g. gitlab-ci and OSSTest exercise this path

I tested this patch successfully with and without xen,static-mem.

---
 xen/arch/arm/domain_build.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 1fbafeaea8..56d3ff9d08 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -874,11 +874,17 @@ static int __init make_memory_node(const struct domain *d,
     if ( mem->nr_banks == 0 )
         return -ENOENT;
 
+    for ( i = 0; i < mem->nr_banks && mem->bank[i].xen_domain; i++ )
+        ;
+    /* No reserved-memory ranges to expose to Dom0 */
+    if ( i == mem->nr_banks )
+        return 0;
+
     dt_dprintk("Create memory node (reg size %d, nr cells %d)\n",
                reg_size, nr_cells);
 
     /* ePAPR 3.4 */
-    snprintf(buf, sizeof(buf), "memory@%"PRIx64, mem->bank[0].start);
+    snprintf(buf, sizeof(buf), "memory@%"PRIx64, mem->bank[i].start);
     res = fdt_begin_node(fdt, buf);
     if ( res )
         return res;
@@ -888,11 +894,14 @@ static int __init make_memory_node(const struct domain *d,
         return res;
 
     cells = &reg[0];
-    for ( i = 0 ; i < mem->nr_banks; i++ )
+    for ( ; i < mem->nr_banks; i++ )
     {
         u64 start = mem->bank[i].start;
         u64 size = mem->bank[i].size;
 
+        if ( mem->bank[i].xen_domain )
+            continue;
+
         dt_dprintk("  Bank %d: %#"PRIx64"->%#"PRIx64"\n",
                    i, start, start + size);
 
-- 
2.25.1