[Xen-devel] [PATCH] xen tracing: Allow tracing to be enabled at boot

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

Add a "tevt_mask" parameter to the xen command-line, allowing
trace records to be gathered early in boot.  They will be placed
into the trace buffers, and read when the user runs "xentrace".

Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>

diff -r 33717472f37e -r 48d08dc25c71 xen/common/trace.c
--- a/xen/common/trace.c        Tue Jun 28 18:15:44 2011 +0100
+++ b/xen/common/trace.c        Thu Jun 30 11:37:20 2011 +0100
@@ -45,7 +45,9 @@ CHECK_t_buf;
 
 /* opt_tbuf_size: trace buffer size (in pages) for each cpu */
 static unsigned int opt_tbuf_size;
+static unsigned int opt_tevt_mask;
 integer_param("tbuf_size", opt_tbuf_size);
+integer_param("tevt_mask", opt_tevt_mask);
 
 /* Pointers to the meta-data objects for all system trace buffers */
 static struct t_info *t_info;
@@ -338,11 +340,21 @@ void __init init_trace_bufs(void)
 {
     register_cpu_notifier(&cpu_nfb);
 
-    if ( opt_tbuf_size && alloc_trace_bufs(opt_tbuf_size) )
+    if ( opt_tbuf_size )
     {
-        printk(XENLOG_INFO "xentrace: allocation size %d failed, disabling\n",
-               opt_tbuf_size);
-        opt_tbuf_size = 0;
+        if ( alloc_trace_bufs(opt_tbuf_size) )
+        {
+            printk("xentrace: allocation size %d failed, disabling\n",
+                   opt_tbuf_size);
+            opt_tbuf_size = 0;
+        }
+        else if ( opt_tevt_mask )
+        {
+            printk("xentrace: Starting tracing, enabling mask %x\n",
+                   opt_tevt_mask);
+            tb_event_mask = opt_tevt_mask;
+            tb_init_done=1;
+        }
     }
 }
 

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