WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

[Xen-devel] [PATCH 1 of 4] xentrace: reduce trace buffer size to somethi

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] [PATCH 1 of 4] xentrace: reduce trace buffer size to something mfn_offset can reach
From: Olaf Hering <olaf@xxxxxxxxx>
Date: Tue, 10 May 2011 16:32:36 +0200
Cc: George Dunlap <george.dunlap@xxxxxxxxxx>
Delivery-date: Tue, 10 May 2011 07:35:30 -0700
Dkim-signature: v=1; a=rsa-sha1; c=relaxed/relaxed; t=1305037957; l=1911; s=domk; d=aepfle.de; h=Cc:To:From:Date:References:In-Reply-To:Subject: Content-Transfer-Encoding:MIME-Version:Content-Type:X-RZG-CLASS-ID: X-RZG-AUTH; bh=LMXENa0U6jtELkzRkdOrIbFkv90=; b=gHyjC6//tIdu88ZbZX1p2h/Glde9A9gXx5SDWcbDr6h1tPcB05cXhGwenam4NKPBUOx 0cSXcNVy2ev3lpX9oepp+8Z8SBBobtoyKrXRMp3LJOTtF36PoS+zniiLnk8JqfwGl08RO WcBY4fX4VX/5HykXlb5PJwSO2Yy3NBFCZiw=
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <patchbomb.1305037955@localhost>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <patchbomb.1305037955@localhost>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mercurial-patchbomb/1.8.1
# HG changeset patch
# User Olaf Hering <olaf@xxxxxxxxx>
# Date 1305037380 -7200
# Node ID 8ac937fa527b28243227193bf4749feb3a234c2c
# Parent  19452acd23045f40c4e18437f0a60f016757e5bd
xentrace: reduce trace buffer size to something mfn_offset can reach

The start of the array which holds the list of mfns for each cpus
tracebuffer is stored in an unsigned short. This limits the total amount
of pages for each cpu as the number of active cpus increases.

Update the math in calculate_tbuf_size() to apply also this rule to the
max number of trace pages. Without this change the index can overflow.

Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>

diff -r 19452acd2304 -r 8ac937fa527b xen/common/trace.c
--- a/xen/common/trace.c        Fri May 06 11:15:35 2011 +0100
+++ b/xen/common/trace.c        Tue May 10 16:23:00 2011 +0200
@@ -112,11 +112,14 @@ static int calculate_tbuf_size(unsigned 
     typeof(dummy_size.prod) max_size;
     struct t_info dummy_pages;
     typeof(dummy_pages.tbuf_size) max_pages;
+    typeof(dummy_pages.mfn_offset[0]) max_mfn_offset;
+    unsigned int max_cpus = num_online_cpus();
     unsigned int t_info_words;
 
     /* force maximum value for an unsigned type */
     max_size = -1;
     max_pages = -1;
+    max_mfn_offset = -1;
 
     /* max size holds up to n pages */
     max_size /= PAGE_SIZE;
@@ -124,6 +127,18 @@ static int calculate_tbuf_size(unsigned 
     if ( max_size < max_pages )
         max_pages = max_size;
 
+    /*
+     * max mfn_offset holds up to n pages per cpu
+     * The array of mfns for the highest cpu can start at the maximum value
+     * mfn_offset can hold. So reduce the number of cpus and also the 
mfn_offset.
+     */
+    max_mfn_offset -= t_info_first_offset - 1;
+    max_cpus--;
+    if ( max_cpus )
+        max_mfn_offset /= max_cpus;
+    if ( max_mfn_offset < max_pages )
+        max_pages = max_mfn_offset;
+
     if ( pages > max_pages )
     {
         printk(XENLOG_INFO "xentrace: requested number of %u pages "

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel