[Xen-devel] Design Session report: Toolstacks

[Xen-devel] Design Session report: Toolstacks

[George Dunlap]

Looking through the notes, it seems like the first part of this
discussion, re hypervisor upgrade / downgrade & libraries, was partly
covered in the distro session, in which Debian's Xen version co-install
was discussed and found useful even if we had a hypervisor , Ian Jackson
agreed to post Debian's co-install patches.

There was a general agreement to improve xl's json handling (including
accepting json to xl create), and a discussion about other improvements;
various people who proposed them seem likely to come back with patches.

 -George

https://hackmd.io/0vZaSrKBT2iKWzpVMxDVvQ

# Xen toolstacks

Issues:
* Hypervisor upgrade / downgrade
* xl not fully-featured
* Remote access

Potential places:
* ~~On top of libxl~~
* Or libxc (symlink swizzling scheme)
    * Doesn't work w/ statically linked
    * Doesn't require HV to deal w/ backwards ABI compatibility
* On the hypervisor
    * Need to keep working for a full release cycle
* A daemon

* xl create w/ json blob
* xl does some processing before passing to libxl

Hypershell has effective golang libxl bindings (but need to be
recompiled against new versions of libxl)

Other wishlist:
* More events (e.g., backend / frontend disconnect)
    * Or, have xl / libxl clean up disconnected entries & notify when done
* Feature parity on other dom0 operating systems







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Re: [Xen-devel] Design Session report: Toolstacks

[Amit Shah]

On Mon, 2019-07-15 at 14:59 +0100, George Dunlap wrote:
> Looking through the notes, it seems like the first part of this
> discussion, re hypervisor upgrade / downgrade & libraries, was partly
> covered in the distro session, in which Debian's Xen version co-
> install
> was discussed and found useful even if we had a hypervisor , Ian
> Jackson
> agreed to post Debian's co-install patches.

Yea.

That's also useful for the live-update project, where we want to (in
the future) use the userspace tools and libraries depending on which
Xen version is in use at a time.

It doesn't need to be much smarter than symlinks for binaries at the
first go, and the symlinks updated each time a live-update operation
succeeds.

Beyond that, for libraries, we'll have to do much smarter things
eventually.



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Re: [Xen-devel] Design Session report: Toolstacks

[George Dunlap]

> On Jul 15, 2019, at 6:57 PM, Amit Shah <amit@infradead.org> wrote:
> 
> On Mon, 2019-07-15 at 14:59 +0100, George Dunlap wrote:
>> Looking through the notes, it seems like the first part of this
>> discussion, re hypervisor upgrade / downgrade & libraries, was partly
>> covered in the distro session, in which Debian's Xen version co-
>> install
>> was discussed and found useful even if we had a hypervisor , Ian
>> Jackson
>> agreed to post Debian's co-install patches.
> 
> Yea.
> 
> That's also useful for the live-update project, where we want to (in
> the future) use the userspace tools and libraries depending on which
> Xen version is in use at a time.

Just to clarify — seems I had an editing fail above; it should have said, “even if we had a stable ABI between the hypervisor and the tools”.  In that case, upgrading to a newer version of Xen but remaining on the same userspace tools should continue to work, and so having multiple versions should be less of an issue (as I presume you’d be unlikely to downgrade in a live update).

But versioned subdirectories and symlinks is definitely something worth doing.

 -George

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