[PATCH v7 2/3] xen/domain: adjust domain ID allocation for Arm

[dmkhn@xxxxxxxxx]

From: Denis Mukhin <dmukhin@xxxxxxxx>

Remove the hardcoded domain ID 0 allocation for hardware domain and replace it
with a call to get_initial_domain_id() (returns the value of hardware_domid on
Arm).

Update domid_alloc(DOMID_INVALID) case to ensure that get_initial_domain_id()
ID is skipped during domain ID allocation to cover domU case in dom0less
configuration. That also fixes a potential issue with re-using ID#0 for domUs
when get_initial_domain_id() returns non-zero.

Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
---
Changes since v6:
- reworked to use bitmap
---
 xen/arch/arm/domain_build.c             | 4 ++--
 xen/common/device-tree/dom0less-build.c | 9 +++------
 xen/common/domain.c                     | 6 ++++++
 3 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index e9d563c269..0ad80b020a 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -2035,9 +2035,9 @@ void __init create_dom0(void)
     if ( !llc_coloring_enabled )
         flags |= CDF_directmap;
 
-    domid = domid_alloc(0);
+    domid = domid_alloc(get_initial_domain_id());
     if ( domid == DOMID_INVALID )
-        panic("Error allocating domain ID 0\n");
+        panic("Error allocating domain ID %d\n", get_initial_domain_id());
 
     dom0 = domain_create(domid, &dom0_cfg, flags);
     if ( IS_ERR(dom0) )
diff --git a/xen/common/device-tree/dom0less-build.c 
b/xen/common/device-tree/dom0less-build.c
index 9236dbae11..8e38affd0c 100644
--- a/xen/common/device-tree/dom0less-build.c
+++ b/xen/common/device-tree/dom0less-build.c
@@ -974,14 +974,11 @@ void __init create_domUs(void)
 
         arch_create_domUs(node, &d_cfg, flags);
 
-        /*
-         * The variable max_init_domid is initialized with zero, so here it's
-         * very important to use the pre-increment operator to call
-         * domain_create() with a domid > 0. (domid == 0 is reserved for Dom0)
-         */
-        domid = domid_alloc(++max_init_domid);
+        domid = domid_alloc(DOMID_INVALID);
         if ( domid == DOMID_INVALID )
             panic("Error allocating ID for domain %s\n", dt_node_name(node));
+        if ( max_init_domid < domid )
+            max_init_domid = domid;
 
         d = domain_create(domid, &d_cfg, flags);
         if ( IS_ERR(d) )
diff --git a/xen/common/domain.c b/xen/common/domain.c
index 37fe811f3f..0145870a7d 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -2424,6 +2424,9 @@ domid_t domid_alloc(domid_t domid)
     }
     else
     {
+        domid_t reserved;
+
+        reserved = __test_and_set_bit(get_initial_domain_id(), domid_bitmap);
         domid = find_next_zero_bit(domid_bitmap, CONFIG_MAX_DOMID,
                                    domid_last);
 
@@ -2439,6 +2442,9 @@ domid_t domid_alloc(domid_t domid)
             __set_bit(domid, domid_bitmap);
             domid_last = domid;
         }
+
+        if ( !reserved )
+            __clear_bit(reserved, domid_bitmap);
     }
 
     spin_unlock(&domid_lock);
-- 
2.34.1