Re: XSA-286, NetBSD and HVM mode

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Sat, Oct 31, 2020 at 10:29:30AM -0400, Greg Troxel wrote:
> 
> There has been a kerfluffle about XSA-286:
> 
>   https://xenbits.xen.org/xsa/advisory-286.html
> 
> which contains the mysterious
> 
>   Note that these patches are known to produce serious performence
>   problems for at least some workloads.  Work is ongoing to improve the
>   performance, and this XSA will be updated when new patches are
>   available.
> 
> 
> I am aware of one VPS provider saying that they aren't applying the
> patches because of these performance problems.  I am also aware of
> a VPS provider saying that "NetBSD does not work under HVM mode".
> 
> 
> Looking at what's in the HOWTO (often edited by me, based on what I know
> and what others tell me, and also edited by others), it says the NetBSD
> domUs can be HVM, without any caveats.
> 
> It also says that PVHVM isn't supported, or PVH.

Both are supported in HEAD, but not in any supported releases.

Unless they have a unusual Xen installation, HVM should work.
Maybe they enforce the use of PV drivers, in which case only HEAD would work.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--