Re: [Xen-devel] reg dom0 console

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2011-11-30 at 01:34 +0000, Prasad B wrote:
> On Wed, Nov 16, 2011 at 8:08 AM, Ian Campbell
> <Ian.Campbell@xxxxxxxxxx> wrote:
>  
>         xl just execs /usr/lib/xen/bin/xenconsole to talk to the
>         console.
>         
>         xenconsole is just a client for xenconsoled which is the
>         daemon which
>         actually consumes guest consoles. The source for both is in
>         tools/console.
>         
>         My memory is fuzzy but IIRC the toolstack writes the
>         keys /local/domain/<DOMID>/console/{ring-ref,port} to xenstore
>         which
>         xenconsoled picks up in order to communicate with the domain.
>         The guest
>         gets its end of things from the startinfo.
> 
> Thanks Ian. We currently have both dom0 and domU versions of MIPS
> Linux up and running. However, we are in the process of connecting to
> domU through xenconsole. In the interim, domU too uses dom0 console
> functions and so the bootup process of domU could be seen. When domU's
> console functions are switched to write to the domU console page, domU
> output (after early printk usage) could not be read through "xl
> console <domId>" command. The sequence of commands are
> 
> xenstored -D
> xenconsoled
> xl create domU.config
> xl console 1
> 
> It was ensured that domU console page and its event channel descriptor
> were allocated correctly in domU.

By allocated do you mean picked up out of the start info? The console
mfn and evtchn for a pv guest are allocated by the builder and put into
the start info rather than the guest making them up/allocating them
itself. You should also see mention of them
in /local/domain/<domid>/console, esp port == evtchn and ring-ref == mfn
(I think) those should match what you pickup within the guest.

What does "xenstore-ls -fp" show?

>  Is there anything else that needs to be plumb the connection between
> dom0 and domU ? Could any other controlled test be run to ensure that
> all the required steps are done ?

You might be able to adapt tools/misc/xen-ringwatch or write your own
simple dom0 utility using libxc to dump the content of the shared ring,
to check if data is making it in there.

Running strace on xencoosled ought to show it polling on /dev/xen/evtch,
waking and doing a read to receive the evtchn notifications but to be
sure you could also instrument drivers/xen/xen-evtchn.c in dom0 to check
if anything was being received/delivered to userspace.

Ian.



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