Re: Can I use SGI's kdb with a dom0 pv-ops kernel?

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Wed, Jun 30, 2010 at 09:44:46AM -0700, Bruce Edge wrote:
> On Wed, Jun 30, 2010 at 9:11 AM, Konrad Rzeszutek Wilk <
> konrad.wilk@oracle.com> wrote:
> 
> > On Tue, Jun 29, 2010 at 03:05:42PM -0700, Bruce Edge wrote:
> > > I asked this a few weeks ago but didn't get a response, so at the risk of
> > > being a nag, I'll abbreviate and restate.
> > >
> > > I know there are other Xen specific debuggers, but I want to know if
> > there's
> > > any reason why SGI's kdb, http://oss.sgi.com/projects/kdb, should not be
> > > included in a dom0 pv-ops kernel?
> >
> > Upstream is integrating one that I think is in 2.6.33
> > or 2.6.34. So when we rev up that we will get it for free.
> >
> 
> Which upstream source is doing this integration? I'm not seeing any
> reference to it on
> 
>  http://kernelnewbies.org/Linux_2_6_33 or
> http://kernelnewbies.org/Linux_2_6_34

I am getting them confused. Here is what I see:

it dc7d552705215ac50a0617fcf51bb9c736255b8e
Author: Jason Wessel <jason.wessel@windriver.com>
Date:   Thu Apr 17 20:05:37 2008 +0200

    kgdb: core
    
    kgdb core code. Handles the protocol and the arch details.


which looks to be in kernel/kgdb.c. You need to have CONFIG_KGDB enabled
for it and some of the Linux command line paramters. That is not the SGI
one but the other one. Is the KGDB not working (or you just are more
comfortable with teh SGI one?)


> > As in, can you use a null modem connection and poke Dom0 via that?
> >
> 
> Yep. The main connection to these boxes is the serial port. The kernel
> cmdline has "console=hvc0,115200n8" so I get boot output on it, I'm using
>  "exec /sbin/getty -8 38400 hvc0" to get a login on the serial console,
> which works fine. The 3xCtrl-A also works.

I wonder if the problem you are hitting is that you are using the hvc0
driver. Not the real serial driver. Which means that the hvc0 driver
isn't picking up any of your input b/c its workqueue has been effectivly
terminated.

One way to go around this is to not use the serial console for Xen and
have the Dom0 use it exclusivly. Which means you would be doing
'console=ttyS0,38400'. At least that is the theory -  I am not sure
if Xen will allow you to do that.