Re: [PATCH 1/3] powerpc: implement barrier primitives

[Will Deacon <will.deacon@arm.com>]

On Thu, Jun 18, 2015 at 10:11:58AM +0100, Michael Ellerman wrote:
> On Wed, 2015-06-17 at 11:15 +0100, Will Deacon wrote:
> > On Wed, Jun 17, 2015 at 10:43:48AM +0100, Andre Przywara wrote:
> > > Instead of referring to the Linux header including the barrier
> > > macros, copy over the rather simple implementation for the PowerPC
> > > barrier instructions kvmtool uses. This fixes build for powerpc.
> > > 
> > > Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> > > ---
> > > Hi,
> > > 
> > > I just took what kvmtool seems to have used before, I actually have
> > > no idea if "sync" is the right instruction or "lwsync" would do.
> > > Would be nice if some people with PowerPC knowledge could comment.
> > 
> > I *think* we can use lwsync for rmb and wmb, but would want confirmation
> > from a ppc guy before making that change!
> 
> Ugh, memory barriers :)

I prefer to call them "Job Security" :)

> You probably can use lwsync, assuming you're only ordering cacheable vs
> cacheable.
> 
> But, lwsync has given us pain in the past[1], so I'd be happier if you just used
> sync.

No probs. I pushed Andre's original patch.

Will