Subject: Re: [PATCH 1/5] powerpc/pseries: do not use msgsndp doorbells on POWER9 guests

From: Benjamin Herrenschmidt <[email-masked]>
Date: Mon, 10 Apr 2017 14:07:38 +1000

On Mon, 2017-04-10 at 13:22 +1000, Nicholas Piggin wrote:
> On Sun, 09 Apr 2017 18:03:35 +1000
> > Benjamin Herrenschmidt <[email-masked]> wrote:
> 
> > On Fri, 2017-04-07 at 22:55 +1000, Nicholas Piggin wrote:
> > > POWER9 hypervisors will not necessarily run guest threads together on
> > > the same core at the same time, so msgsndp should not be used.  
> > 
> > Maybe we shouldn't advertise doorbells at all ?
> 
> Possibly not. I don't know if there is a good way to switch it off
> in the guest from the host with device tree currently. Might be better
> to clear it early in the guest rather than test it here though?

Sure for now. Long term a separate DT entry would be good. Might be
worth re-enabling one day if we have HW virtualization of geust
doorbells.

Cheers,
Ben