On x86, Xen does not claim any serial port unless the user

explicitly specifies a 'com1=' or 'com2=' configuration
string. This prevents users from being surprised when Xen
stops domain0 from accessing serial port registers.

On ia64 we still allow serial ports to get automatically
configured and locked down even if no 'com1' is specified
on the command line. This maintains the default preferred
by the IA64 developers.

Also, the method for specifying 'use existing baud rate'
has changed. Instead of specifying com1=0, you must now
specify e.g., com1=auto

Signed-off-by: Keir Fraser <keir@xensource.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/docs/src/user.tex b/docs/src/user.tex
index 32c0decde7..da41a813dc 100644
--- a/docs/src/user.tex
+++ b/docs/src/user.tex
@@ -1709,8 +1709,11 @@ editing \path{grub.conf}.
  For example: `com1=9600, 8n1, 0x408, 5' maps COM1 to a
  9600-baud port, 8 data bits, no parity, 1 stop bit,
  I/O port base 0x408, IRQ 5.
- If the I/O base and IRQ are standard (com1:0x3f8,4;
- com2:0x2f8,3) then they need not be specified. 
+ If some configuration options are standard (e.g., I/O base and IRQ),
+ then only a prefix of the full configuration string need be
+ specified. If the baud rate is pre-configured (e.g., by the
+ bootloader) then you can specify `auto' in place of a numeric baud
+ rate. 
 
 \item [console=$<$specifier list$>$ ] 
  Specify the destination for Xen console I/O.