doc, xen: Mention 'earlyprintk=xen' in the documentation.

commit 2482a92e7d upstream.

The earlyprintk for Xen PV guests utilizes a simple hypercall
(console_io) to provide output to Xen emergency console.

Note that the Xen hypervisor should be booted with 'loglevel=all'
to output said information.

Reported-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Link: http://lkml.kernel.org/r/1361825650-14031-2-git-send-email-konrad.wilk@oracle.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Konrad Rzeszutek Wilk 2013-02-25 15:54:08 -05:00 committed by Greg Kroah-Hartman
parent 92916fb21c
commit 938987dc41

View file

@ -742,6 +742,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
earlyprintk= [X86,SH,BLACKFIN]
earlyprintk=vga
earlyprintk=xen
earlyprintk=serial[,ttySn[,baudrate]]
earlyprintk=ttySn[,baudrate]
earlyprintk=dbgp[debugController#]
@ -759,6 +760,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
The VGA output is eventually overwritten by the real
console.
The xen output can only be used by Xen PV guests.
ekgdboc= [X86,KGDB] Allow early kernel console debugging
ekgdboc=kbd