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Re: [Xen-devel] [PATCH] 14287 followup - console

Sounds like a plan...

How about this ?


Keir Fraser wrote:
On 13/3/07 12:24, "Ben Thomas" <bthomas@xxxxxxxxxxxxxxx> wrote:

Two input sources are inherently capable
of getting slightly out of sync (or worse).  The second reason
is that syslog can be expensive.  In the end, the WYSIWYG and
cost resulted in the console ring approach.

Would this be more acceptable if it were selectable ?  That is,
come up with a libxc/sysctl mechanism (which should be pretty
easy) to control the gating of character data to the console ring
fom guest_console_write ?

You could add a Xen boot parameter.

 -- Keir

Ben Thomas                                         Virtual Iron Software
bthomas@xxxxxxxxxxxxxxx                            Tower 1, Floor 2
978-849-1214                                       900 Chelmsford Street
                                                   Lowell, MA 01851
Add boot option to allow console I/O to be placed into ring buffer

This option allows console I/O to be placed into the hypervisor
console ring buffer. When enabled, all output to the console
device will be reflected in the ring buffer.  When disabled (the
default), only hypervisor output is available from the ring

Signed-off-by: Ben Thomas (ben@xxxxxxxxxxxxxxx)

diff -r f183e0a4d0c9 docs/src/user.tex
--- a/docs/src/user.tex Wed Mar 14 08:32:05 2007 -0400
+++ b/docs/src/user.tex Wed Mar 14 08:35:11 2007 -0400
@@ -3179,6 +3179,11 @@ editing \path{grub.conf}.
   one of 80x25, 80x28, 80x30, 80x34, 80x43, 80x50, 80x60.
   \item[ keep ] Keep the VGA console even after domain 0 boots.
+\item [ console\_to\_ring ] Place guest console output into the
+  hypervisor console ring buffer. This is disabled by default.
+  When enabled, both hypervisor output and guest console output
+  is available from the ring buffer. This can be useful for logging
+  and/or remote presentation of console data.
 \item [ sync\_console ] Force synchronous console output. This is
   useful if you system fails unexpectedly before it has sent all
   available output to the console. In most cases Xen will
diff -r f183e0a4d0c9 xen/drivers/char/console.c
--- a/xen/drivers/char/console.c        Wed Mar 14 08:32:05 2007 -0400
+++ b/xen/drivers/char/console.c        Wed Mar 14 08:32:06 2007 -0400
@@ -48,6 +48,10 @@ static int opt_sync_console;
 static int opt_sync_console;
 boolean_param("sync_console", opt_sync_console);
+/* console_to_ring: send guest (incl dom 0) console data to console ring */
+static int opt_console_to_ring;
+boolean_param("console_to_ring", opt_console_to_ring);
 #define CONRING_SIZE 16384
 #define CONRING_IDX_MASK(i) ((i)&(CONRING_SIZE-1))
 static char conring[CONRING_SIZE];
@@ -328,8 +332,14 @@ static long guest_console_write(XEN_GUES
-        for ( kptr = kbuf; *kptr != '\0'; kptr++ )
+        for ( kptr = kbuf; *kptr != '\0'; kptr++ ) {
+            if (opt_console_to_ring)
+                putchar_console_ring(*kptr);
+        }
+        if (opt_console_to_ring)
+            send_guest_global_virq(dom0, VIRQ_CON_RING);
         guest_handle_add_offset(buffer, kcount);
         count -= kcount;
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