[PATCH 1 of 5] xentrace: fix t_info_pages calculation for the default case

[Olaf Hering <olaf@aepfle.de>]

# HG changeset patch
# User Olaf Hering <olaf@aepfle.de>
# Date 1300813685 -3600
# Node ID 08df96398bff82a8924a37eda6ddffd1ada3f407
# Parent  c81f0ef5a77d90fbf108d3efe489d08df45b63c2
xentrace: fix t_info_pages calculation for the default case

The default tracebuffer size of 32 pages was not tested with the previous patch.
As a result, t_info_pages will become zero and alloc_xenheap_pages() fails.
Catch this case and allocate at least one page.

Signed-off-by: Olaf Hering <olaf@aepfle.de>

diff -r c81f0ef5a77d -r 08df96398bff xen/common/trace.c
--- a/xen/common/trace.c	Mon Mar 21 14:52:27 2011 +0000
+++ b/xen/common/trace.c	Tue Mar 22 18:08:05 2011 +0100
@@ -125,7 +125,7 @@
     t_info_pages = num_online_cpus() * pages + t_info_first_offset;
     t_info_pages *= sizeof(uint32_t);
     t_info_pages /= PAGE_SIZE;
-    if ( t_info_pages % PAGE_SIZE )
+    if ( t_info_pages % PAGE_SIZE || t_info_pages == 0 )
         t_info_pages++;
     return pages;
 }