[Xen-changelog] [xen-unstable] xentrace: correct formula to calculate t_info_pages

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Olaf Hering <olaf@xxxxxxxxx>
# Date 1301755819 -3600
# Node ID 4a335f1000eaaa2a7994e7a78f17d6f7b5f64191
# Parent  1046830079376a4b29fcad0cd037a834e808ed06
xentrace: correct formula to calculate t_info_pages

The current formula to calculate t_info_pages, based on the initial
code, is slightly incorrect. It may allocate more than needed.
Each cpu has some pages/mfns stored as uint32_t.
That list is stored with an offset at tinfo.

Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
Acked-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
---


diff -r 104683007937 -r 4a335f1000ea xen/common/trace.c
--- a/xen/common/trace.c        Sat Apr 02 15:49:25 2011 +0100
+++ b/xen/common/trace.c        Sat Apr 02 15:50:19 2011 +0100
@@ -110,7 +110,7 @@
 {
     struct t_buf dummy;
     typeof(dummy.prod) size;
-    unsigned int t_info_words, t_info_bytes;
+    unsigned int t_info_words;
 
     /* force maximum value for an unsigned type */
     size = -1;
@@ -125,9 +125,8 @@
         pages = size;
     }
 
-    t_info_words = num_online_cpus() * pages + t_info_first_offset;
-    t_info_bytes = t_info_words * sizeof(uint32_t);
-    t_info_pages = PFN_UP(t_info_bytes);
+    t_info_words = num_online_cpus() * pages * sizeof(uint32_t);
+    t_info_pages = PFN_UP(t_info_first_offset + t_info_words);
     printk(XENLOG_INFO "xentrace: requesting %u t_info pages "
            "for %u trace pages on %u cpus\n",
            t_info_pages, pages, num_online_cpus());

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