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From: Havoc Pennington <hp@pobox.com>
Date: Fri, 17 Apr 2015 16:27:27 -0400
Message-ID: <CAEntwhGcDJvnL-S9VxFqE3UxKcR-9PjVqzSZ=8YpLTzXfhUm9g@mail.gmail.com>
Subject: Re: [GIT PULL] kdbus for 4.1-rc1
To: James Bottomley <James.Bottomley@hansenpartnership.com>
Cc: David Herrmann <dh.herrmann@gmail.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Kosina <jkosina@suse.cz>, Steven Rostedt <rostedt@goodmis.org>,
        John Stoffel <john@stoffel.org>, Andy Lutomirski <luto@amacapital.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Arnd Bergmann <arnd@arndb.de>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>,
        Tom Gundersen <teg@jklm.no>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Daniel Mack <daniel@zonque.org>, Djalal Harouni <tixxdz@opendz.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
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Hi,

On Fri, Apr 17, 2015 at 3:27 PM, James Bottomley
<James.Bottomley@hansenpartnership.com> wrote:
>
> This is why I think kdbus is a bad idea: it solidifies as a linux kernel
> API something which runs counter to granular OS virtualization (and
> something which caused Windows to fall behind Linux in the container
> space).  Splitting out the acceleration problem and leaving the rest to
> user space currently looks fine because the ideas Al and Andy are
> kicking around don't cause problems with OS virtualization.
>

I'm interested in understanding this problem (if only for my own
curiosity) but I'm not confident I understand what you're saying
correctly.

Can I try to explain back / ask questions and see what I have right?

I think you are saying that if an application relies on a system
service (= any other process that runs on the system bus) then to
virtualize that app by itself in a dedicated container, the system bus
and the system service need to also be in the container. So the
container ends up with a bunch of stuff in it beyond only the
application.  Right / wrong / confused?

I also think you're saying that userspace dbus has the same issue
(this isn't a userspace vs. kernel thing per se), the objection to
kdbus is that it makes this issue more solidified / harder to fix?

Do you have ideas on how to go about fixing it, whether in userspace
or kernel dbus?

Havoc
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