Re: [Xen-devel] Xen 4.2 new features and status -- please help me make a list

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-09-07 at 15:34 +0100, Andres Lagar-Cavilla wrote:

> > xenpaging: Page HVM guest pages to disk
> >        Was marked as tech preview in 4.1 and earlier, still is?
> > 
> > memsharing: Sharing of HVM guest pages.
> >        Was marked as tech preview in 4.1 and earlier, still is?
> 
> Both xenpaging and memsharing are functional as far as I am concerned.

This is on the hypervisor side I guess? Or are the tools as supplied in
the xen tree useful too?

It's a tricky one in terms of how to describe it on xen.org if not. I'd
be inclined to go "yes" on the basis of the hypervisor side being solid,
apart from the two caveats you then mention below (mainly the border
conditions one).

>  Intel EPT is the platform of choice. There are many reports of
> success on AMD insofar xenpaging goes, but I haven't gotten good
> traction with either xen{paging/sharing} on AMD. 
> 
> Please note that memsharing has been significantly overhauled both at
> an interface and internals level. It bears almost no resemblance to
> the 4.1 release.

I'll mention that somewhere too.

> Xen{paging/sharing} still have border conditions in which domains are
> crashed. They are rare enough that I have not experienced them in
> practice. This is due to a need for more mature wait queue code in the
> hypervisor. The plan is to address this in 4.3.

Perhaps that's an argument for leaving it as tech-preview until 4.3
then?

> Finally, mem-access has seen improvements and extensions. Now you can
> get a log of all memory accesses by a guest (if you so wished) using
> the n2rwx mode.

thanks, I'll be sure to mention that.

Ian.


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