Re: console: introduce console=none option

[Tim Deegan <tim@xen.org>]

At 16:00 +0000 on 26 Jan (1327593636), Jan Beulich wrote:
> >>> On 26.01.12 at 15:58, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
> > On 26/01/12 14:41, Jan Beulich wrote:
> >>>>> On 26.01.12 at 13:19, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
> >>> XenServer by default boots without a serial console (buggy hardware
> >>> reasons) and dom0 displays a splash screen.  Unfortunately, having Xen
> >>> writing to the vga text area looks ugly whilst dom0 is trying to set up
> >>> non-text mode and display  the splash screen.
> >>>
> >>> We have been using "console=" to prevent this behavior for a while, but
> >>> presented herewith is a patch to fix the problem correctly.
> >> While I don't mind the patch, I'm completely confused by the description:
> >> Where is it that Xen writes to VGA text area after control was passed to
> >> Dom0?
> >>
> >> Jan
> > 
> > I have not debugged it that much as I was looking for a clean solution
> > to our current hack of "console=" (and I have some rather more serious
> > deadlock bugs to debug), but it all Xen printk's are going into the VGA
> > text area, even after dom0 has started.  It is possible that Xen is
> > still writing into the text area after dom0 has switched VGA mode, but I
> > have no proof of this one way or the other.
> 
> Just take a look at vga_endboot() - the output routine gets pointed to
> vga_noop_puts() unless vgacon_keep. Beyond that point nothing
> can possibly get printed to the VGA text screen, or if it does, then I'd
> suspect there's some other change in XenServer that makes it so.

IIRC in some XenServer versions the bootloader also puts up a
splashscreen; that may be causing some confusion.

Tim.