Re: [Xen-devel] [PATCH RFC 00/15] dom0less step1: boot multiple domains from device tree

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 14 Jun 2018, Edgar E. Iglesias wrote:
> On Wed, Jun 13, 2018 at 03:15:09PM -0700, Stefano Stabellini wrote:
> > Hi all,
> > 
> > This is first step toward "dom0less" as discussed in the various
> > certifications related threads and discussions.
> > 
> > The goal of this series is to enable Xen to boot multiple domains in
> > parallel, in addition to dom0, out of information found on device tree.
> > 
> > The device tree based boot protocol is extended to carry information
> > about DomUs. Based on that information, Xen creates and starts one or
> > more DomUs. DomUs created this way don't have access to xenstore, as
> > xenstore is not started yet. This is actually OK, because this is meant
> > for mission critical applications that typically only access directly
> > assigned devices. They cannot tolerate interference or increased IRQ
> > latency due to PV protocols. Device assignment is not actually covered
> > by this series, it will be added later.
> > 
> > DomUs can print to the Xen serial using the CONSOLEIO hypercalls. A
> > virtual PL011 is also emulated for them so that they can use their
> > regular PL011 driver. This allows unmodified guests to run as Xen on ARM
> > guests -- no Xen support needed at all. Console input also comes from
> > the Xen serial: the Ctrl-AAA switching mechanism is extended to switch
> > among domUs, dom0, and Xen.
> 
> Hi Stefano,
> 
> I think this looks very promising!
> 
> A question, do you have any thoughts on how we in the long run could
> try to keep xl configs somewhat on par with the format here?
> 
> Or would the device-tree naming of options eventually have to diverge.
> 
> Eventually we'll need support for describing arbitrary memory maps and
> device passthrough via device-tree for these domUs.

I think it makes sense to try to keep the two set of options somewhat
similar. I am keen on minimizing meaningless differences between the
two. Especially arbitrary memory maps and device passthrough
configurations, that are complex options -- it is worth trying to keep
them the same.

However, in general, I don't think we can promise to keep them exactly
identical. There are a lot of xl config options that won't be supported
as part of device tree booting. And when they are supported, there might
be additional parameters that are ignored.
docs/misc/arm/device-tree/booting.txt will be the official doc for
device tree booting options, while docs/man/xl.cfg.pod.5 will be the
official doc for xl config file options.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel