Re: [Xen-devel] [GIT PULL] remove xend for 4.5 (Was: Re: [PATCH] MAINTAINERS: Exclude xend from toolstack maintainers entry)

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2014-03-27 at 12:03 +0000, George Dunlap wrote:
> On Thu, Mar 27, 2014 at 11:18 AM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> 
> wrote:
> > On Thu, 2014-03-27 at 11:08 +0000, George Dunlap wrote:
> >> On Thu, Mar 27, 2014 at 11:00 AM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> 
> >> wrote:
> >> On my list of dependencies for removing xend, I have the following:
> >>
> >> * xend still in tree (x)
> >>  - xl list -l on a dom0-only system
> >
> > Not sure what this was, doesn't sound either hard or critical though.
> 
> This is from an e-mail from Konrad, msd-id
> <20130904140414.GA3188@xxxxxxxxxxxxxxxxxxx> .  He said:
> 
> - No status in xl list -l when only dom0 is present.
> 
> I'm not sure exactly what that means.  On my system, "xl list -l" on a
> system with no domUs running produces an empty, but valid, array -- "[
> ]".  (With some extra whitespace.)
> 
> Looking further in the thread, it looks like Wei took a look at this,
> and that at the moment "xl list -l" depends on reading the config file
> from disk, which is a bigger architectural issue that needs to be
> resolved.  You posted a PoC patch that you had started, but obviously
> it hasn't been upstreamed yet.
> 
> So this should probably actually be "xl list -l contains no
> information for dom0".

I think Wei was going to work on this again shortly IIRC from our
discussion last week.

> >>  - xl list -l doesn't contain tty console port
> >
> > I think this was fixed, wasn't it (assuming I understand what it
> > actually means).
> >
> >>  - xl Alternate transport support for migration*
> >
> > What is this?
> 
> From another section of my to-do list:
> 
> * xl migrate transport improvements
>  owner: None
>  > See discussion here: http://bugs.xenproject.org/xen/bug/19
>  - Option to connect over a plain TCP socket rather than ssh
>  - xl-migrate-recieve suitable for running in inetd
>  - option for above to redirect log output somewhere useful
>  - Documentation for setting up alternate transports

http://bugs.xenproject.org/xen/bug/18 might be something of a duplicate
of this.

It's not clear what this has to do with xend though, it looks like a
wishlist feature request for xl to me, but one that has no relationship
with xend.

> 
> OTOH, as a result of that discussion, it became clear that:
> 1. xl did have the ability to use socat / ssl; the command-line
> arguments to do that are a bit wonky, however, and the documentation
> is far from clear
> 2. The system envisioned was terribly insecure.  Receiving a domain at
> the moment allows the sender trivial access to all files on the system
> (including your root disk); receiving domains without authenticating
> the sender means implicit trust of the entire control network.
> 
> So perhaps this wouldn't be a blocker.

Indeed, not even close IMHO.

> >>  - xl support for vnc and vnclisten options with PV guests
> >
> > Wei fixed this already, in 4.4 even perhaps.
> >
> >> - xl PVSCSI support
> >> - xl PVUSB support
> >
> > Meh.
> >
> > Any of the above which are still issues can still be considered to
> > become blockers for 4.5, that doesn't necessarily imply they should
> > block removal of xend.
> >
> > I think at some point we just have to rip the plaster off and I think
> > that time is now. Doing so will provide additional impetus to actually
> > fix any remaining issues, as it stands things have stagnated because
> > people just think "oh, it's ok xend is still available".
> 
> FWIW, back in September when we had this discussion, Olaf and Jan both
> said they still had customers using PVSCSI.  I responded:
> 
>  "...at some point, if it's not important enough for someone to
> implement, it's not important enough to keep supporting."
> 
> To which Jan replied, "I accept that this is one way of viewing
> things, but as someone implementing hypervisor side stuff for people
> even if neither I nor customers of my employer immediately need it, I
> think it is not completely off to expect some symmetry here: I think
> it is reasonable for someone to point out deficiencies in areas (s)he
> doesn't normally work on, and expect those responsible for these areas
> to pick this up unless it's completely off."
> 
> And I think he has a point.

True. 

It looks like Olaf has this in hand though.

> So what about the following dependency list?
> 
> * xend still in tree
>  [blocker]

NB: I would consider these blockers for 4.5, *not* blockers for removing
xend.

>  - xl list -l doesn't contain information about dom0
>  - xl PVSCSI support
>  [nice-to-have]
>  - xl Alternate transport support for migration*
>  - xl PVUSB support
>  [fixed]
>  - xl list -l doesn't contain tty console port
>  - xl support for vnc and vnclisten options with PV guests
> 
>  -George



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