Re: [PATCH 3/3] x86/xen: Move paravirt IOPL switching to slow the path

[Andy Lutomirski]

On Wed, Jun 14, 2017 at 5:40 AM, Brian Gerst <brgerst@xxxxxxxxx> wrote:
> Since tasks using IOPL are very rare, move the switching code to the slow
> path for lower impact on normal tasks.

I think that Andrew Cooper added a vmassist that we could opt in to
that makes Xen PV IOPL switching work more or less just like native.
We could maybe opt in to that and avoid needing this stuff at all on
newer hypervisors.