Re: [Xen-devel] Future of 32-bit PV support

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.08.18 at 08:17, <jgross@xxxxxxxx> wrote:
> In the Xen x86 community call we have been discussing whether anyone
> really is depending on 32-bit PV guests. We'd like to evaluate whether
> anyone would see problems with:
> 
> - deprecating 32-bit PV guest support in Xen, meaning that we'd
>   eventually switch to support 32-bit PV guests only via PV-shim from
>   Xen 4.12 or 4.13

I think we shouldn't try to be too eager here. Deprecating is fine if
we can get sufficient confirmation that no-one needs this anymore,
but switching to something like the shim-only model needs to come
sufficiently much later.

For people concerned about memory footprint, should we perhaps
make x32 support in public headers and tool stack a prereq here?
Not the least because - afaict - 32-bit user space support in 64-bit
Linux continues to be subtly broken, due to there not being any
clear route for what to do with "x86-64/Xen: fix stack switching",
sent over three months ago? But even without that I think x32 is
preferable over true 32-bit mode.

Jan

> - dropping 32-bit PV support from upstream Linux kernel, resulting in
>   current 32-bit PV guests no longer being able to upgrade to the newest
>   kernel version any longer
> 
> And related to that:
> 
> - is there any Linux distribution still shipping 32-bit PV-capable
>   systems?
> 
> - what about BSD? Is 32-bit PV support important there?
> 
> 
> Juergen
> 
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