Re: Mirage Xenstore Stub Domain

[Dave Scott <Dave.Scott@xxxxxxxxxxxxx>]

Hi,

Last time I looked at xen-unstable there was a proposal to make the xenstore 
domain builder (is that init-xenstore-domain?) itself daemonise and drain the 
console ring, since xenconsoled can't work in the normal way. I've not followed 
the discussion closely since, maybe they came up with another solution? It's 
worth a quick mailing list archive search.

So I agree an emergency console ring is useful (actually I was going to write 
logs to it for now) and it should be possible...

Btw why is write_all causing us to spin on the CPU? Surely we would just block 
if the console ring wasn't being drained? Suspicious...

-- 
Dave Scott

On Jul 15, 2013, at 11:40 PM, "Anil Madhavapeddy" <anil@xxxxxxxxxx> wrote:

> It would certainly be nicer to arrange for the Xenstore stub domain to have 
> access to an emergency console ring in this case.  Is there a Xenconsoled 
> stub domain too, Dave, or would this have to be the hypervisor console ring?
> 
> -anil
> 
> On 15 Jul 2013, at 22:59, James Bielman <jamesjb@xxxxxxxxx> wrote:
> 
>> I've hit another snag with the Xenstore stub domain.  I've built 
>> "ocaml-xenstore-xen" with Mirari, and I'm launching it early in the dom0 
>> boot process with "init-xenstore-domain".  The xenstore kernel seems to hang 
>> with 100% CPU usage trying to write to the console (which makes some sense 
>> to me, since nothing is reading from the ring buffer yet).  My guess is that 
>> the loop in "OS.Console.write_all" is the culprit---if I stub this function 
>> out to return zero, it starts up and works just fine.
>> 
>> I've been trying to figure out if this is a bootstrapping issue that's 
>> somewhat unavoidable or a bug, but I don't yet have enough of a handle on 
>> how LWT works to be sure.
>> 
>> James
>> 
>> 
>> 
>> On Mon, Jul 8, 2013 at 4:25 PM, James Bielman <jamesjb@xxxxxxxxx> wrote:
>> Thanks! It builds for me now after following your process and hacking up a 
>> quick and dirty mirari config file.
>> 
>> Cheers,
>> James
>> 
>> 
>> On Mon, Jul 8, 2013 at 3:10 PM, David Scott <scott.dj@xxxxxxxxx> wrote:
>> Hi James,
>> 
>> I think you're right -- some key interfaces have changed. Since some of the 
>> changes are fairly fresh in my memory, I did a first pass at fixing the code.
>> 
>> The blog post is a bit out of date now. The best way to start is to:
>> 
>> opam init
>> opam switch 4.00.1
>> opam remote add xapi-project git://github.com/xapi-project/opam-repo-dev
>> opam remote add mirage git://github.com/mirage/opam-repo-dev
>> opam install mirage-xen xenstore
>> 
>> and then clone the repo and build in the 'xen' directory. For me the files 
>> compile but fail to link. The next thing to do is to investigate using the 
>> 'mirari' tool to link a xen kernel, like the other examples in the 
>> mirage/mirage-skeleton repo. This is fallout from the recent (very good 
>> IMHO) change to avoid using a special 'opam compiler switch' to install 
>> mirage kernels. You can now use a regular (unpatched) compiler and link in 
>> the 'mirage-xen' package.
>> 
>> Sorry for the build breakage!
>> 
>> Cheers
>> Dave
>> 
>> 
>> On Mon, Jul 8, 2013 at 10:10 PM, James Bielman <jamesjb@xxxxxxxxx> wrote:
>> Hi all,
>> 
>> I am attempting to build the Mirage Xenstore stub domain by following these 
>> instructions on the Mirage blog:
>> 
>>  http://www.openmirage.org/blog/xenstore-stub-domain
>> 
>> However, I'm running into some trouble---it looks like the interfaces for 
>> shared memory rings and grant tables have changed since the 
>> "xs_transport_domain" module was written.  I'm using Mirage as installed 
>> from "opam" and the "ocaml-xenstore-xen" module from the Git  repository at:
>> 
>>   git://github.com/djs55/ocaml-xenstore-xen
>> 
>> Is there is an updated repository elsewhere that works with the latest 
>> Mirage?  If not, I may take a stab at bringing it up to date, and would 
>> appreciate any insight available on gotchas I might run into.
>> 
>> Thanks,
>> James
>> 
>> 
>> 
>> 
>> -- 
>> Dave Scott
> 
>