sysctl: adjust XEN_SYSCTL_cputopoinfo behavior

The new function's implementation, unlike the original one of
XEN_SYSCTL_topologyinfo, didn't allow the caller to get what it needs
(if e.g. it's after the data for just one specific CPU) with just one
hypercall, without caring about the total number of CPUs in the system.

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

diff --git a/xen/common/sysctl.c b/xen/common/sysctl.c
index 601dd09130030e196f1b0d21ae9b8a0606c02ca3..5f9af2b294641ca7d7ba845f66417ca76370da5f 100644 (file)
--- a/xen/common/sysctl.c
+++ b/xen/common/sysctl.c
@@ -358,15 +358,9 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xen_sysctl_t) u_sysctl)
         {
             xen_sysctl_cputopo_t cputopo = { 0 };
 
-            if ( ti->num_cpus < num_cpus )
-            {
-                ret = -ENOBUFS;
-                i = num_cpus;
-            }
-            else
-                i = 0;
-
-            for ( ; i < num_cpus; i++ )
+            if ( num_cpus > ti->num_cpus )
+                num_cpus = ti->num_cpus;
+            for ( i = 0; i < num_cpus; ++i )
             {
                 if ( cpu_present(i) )
                 {
@@ -393,7 +387,7 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xen_sysctl_t) u_sysctl)
         else
             i = num_cpus;
 
-        if ( (!ret || (ret == -ENOBUFS)) && (ti->num_cpus != i) )
+        if ( !ret && (ti->num_cpus != i) )
         {
             ti->num_cpus = i;
             if ( __copy_field_to_guest(u_sysctl, op,

diff --git a/xen/include/public/sysctl.h b/xen/include/public/sysctl.h
index cd544c0ef479e60b28e9b479b638bad361f025d4..86de43807a0715adbf494450baa8857c6dd95ef6 100644 (file)
--- a/xen/include/public/sysctl.h
+++ b/xen/include/public/sysctl.h
@@ -482,10 +482,11 @@ DEFINE_XEN_GUEST_HANDLE(xen_sysctl_cputopo_t);
  *  - otherwise it's the number of entries in 'cputopo'
  *
  * OUT:
- *  - If 'num_cpus' is less than the number Xen needs to write, -ENOBUFS shall
- *    be returned and 'num_cpus' updated to reflect the intended number.
- *  - On success, 'num_cpus' shall indicate the number of entries written, which
- *    may be less than the maximum.
+ *  - If 'num_cpus' is less than the number Xen wants to write but the handle
+ *    handle is not a NULL one, partial data gets returned and 'num_cpus' gets
+ *    updated to reflect the intended number.
+ *  - Otherwise, 'num_cpus' shall indicate the number of entries written, which
+ *    may be less than the input value.
  */
 struct xen_sysctl_cputopoinfo {
     uint32_t num_cpus;