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

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 <[email protected]>
Signed-off-by: Konrad Rzeszutek Wilk <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Cc: <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>
This commit is contained in:
Konrad Rzeszutek Wilk 2013-02-25 15:54:08 -05:00 • committed by H. Peter Anvin
commit 2482a92e7d

View file

@ -754,6 +754,7 @@ 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#]
@ -771,6 +772,8 @@ 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