sysctl: adjust XEN_SYSCTL_numainfo behavior

... to match XEN_SYSCTL_cputopoinfo, allowing the caller to get what it
needs (if e.g. it's after the data for just one specific node) with
just one hypercall, without caring about the total number of nodes in
the system.

Suggested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Dario Faggioli <dario.faggioli@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

diff --git a/xen/common/sysctl.c b/xen/common/sysctl.c
index 5f9af2b294641ca7d7ba845f66417ca76370da5f..f1c0c76e7977259ad812a124392b2bf3419fffae 100644 (file)
--- a/xen/common/sysctl.c
+++ b/xen/common/sysctl.c
@@ -285,15 +285,9 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xen_sysctl_t) u_sysctl)
         {
             xen_sysctl_meminfo_t meminfo = { 0 };
 
-            if ( ni->num_nodes < num_nodes )
-            {
-                ret = -ENOBUFS;
-                i = num_nodes;
-            }
-            else
-                i = 0;
-
-            for ( ; i < num_nodes; i++ )
+            if ( num_nodes > ni->num_nodes )
+                num_nodes = ni->num_nodes;
+            for ( i = 0; i < num_nodes; ++i )
             {
                 static uint32_t distance[MAX_NUMNODES];
 
@@ -335,7 +329,7 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xen_sysctl_t) u_sysctl)
         else
             i = num_nodes;
 
-        if ( (!ret || (ret == -ENOBUFS)) && (ni->num_nodes != i) )
+        if ( !ret && (ni->num_nodes != i) )
         {
             ni->num_nodes = i;
             if ( __copy_field_to_guest(u_sysctl, op,

diff --git a/xen/include/public/sysctl.h b/xen/include/public/sysctl.h
index 86de43807a0715adbf494450baa8857c6dd95ef6..58c9be254be8b5a98723fefcfb0e57573b786fb9 100644 (file)
--- a/xen/include/public/sysctl.h
+++ b/xen/include/public/sysctl.h
@@ -515,10 +515,11 @@ DEFINE_XEN_GUEST_HANDLE(xen_sysctl_meminfo_t);
  *    non-null)
  *
  * OUT:
- *  - If 'num_nodes' is less than the number Xen needs to write, -ENOBUFS shall
- *    be returned and 'num_nodes' updated to reflect the intended number.
- *  - On success, 'num_nodes' shall indicate the number of entries written, which
- *    may be less than the maximum.
+ *  - If 'num_nodes' is less than the number Xen wants to write but either
+ *    handle is not a NULL one, partial data gets returned and 'num_nodes'
+ *    gets updated to reflect the intended number.
+ *  - Otherwise, 'num_nodes' shall indicate the number of entries written, which
+ *    may be less than the input value.
  */
 
 struct xen_sysctl_numainfo {