[PATCH v2 5/5] libxc/PM: Retry get_pxstat if data is incomplete

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

If the total returned by Xen is more than the number of elements
allocated, it means that the buffer was too small and so the data is
incomplete. Retry to get all the data.

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
---

* New in v2.

 tools/misc/xenpm.c | 49 +++++++++++++++++++++++++++++-----------------
 1 file changed, 31 insertions(+), 18 deletions(-)

diff --git a/tools/misc/xenpm.c b/tools/misc/xenpm.c
index de319329e6b0..d5387f5f0693 100644
--- a/tools/misc/xenpm.c
+++ b/tools/misc/xenpm.c
@@ -312,29 +312,42 @@ static int get_pxstat_by_cpuid(xc_interface *xc_handle, 
int cpuid, struct xc_px_
     int ret = 0;
     int max_px_num = 0;
 
-    ret = xc_pm_get_max_px(xc_handle, cpuid, &max_px_num);
-    if ( ret )
-        return -errno;
-
     if ( !pxstat)
         return -EINVAL;
 
-    pxstat->total = max_px_num;
-    pxstat->trans_pt = malloc(max_px_num * max_px_num *
-                              sizeof(uint64_t));
-    if ( !pxstat->trans_pt )
-        return -ENOMEM;
-    pxstat->pt = malloc(max_px_num * sizeof(struct xc_px_val));
-    if ( !pxstat->pt )
+    for ( ; ; )
     {
-        free(pxstat->trans_pt);
-        return -ENOMEM;
-    }
+        ret = xc_pm_get_max_px(xc_handle, cpuid, &max_px_num);
+        if ( ret )
+            return -errno;
 
-    ret = xc_pm_get_pxstat(xc_handle, cpuid, pxstat);
-    if( ret )
-    {
-        ret = -errno;
+        pxstat->total = max_px_num;
+        pxstat->trans_pt = malloc(max_px_num * max_px_num *
+                                  sizeof(uint64_t));
+        if ( !pxstat->trans_pt )
+            return -ENOMEM;
+        pxstat->pt = malloc(max_px_num * sizeof(struct xc_px_val));
+        if ( !pxstat->pt )
+        {
+            free(pxstat->trans_pt);
+            return -ENOMEM;
+        }
+
+        ret = xc_pm_get_pxstat(xc_handle, cpuid, pxstat);
+        if ( ret )
+        {
+            ret = -errno;
+            free(pxstat->trans_pt);
+            free(pxstat->pt);
+            pxstat->trans_pt = NULL;
+            pxstat->pt = NULL;
+            break;
+        }
+
+        if ( pxstat->total <= max_px_num )
+            break;
+
+        /* get_max_px changed under our feet so the data is incomplete. */
         free(pxstat->trans_pt);
         free(pxstat->pt);
         pxstat->trans_pt = NULL;
-- 
2.49.0