linux-kernel - Re: [PATCH v2 0/3] x86: faster mb()+other barrier.h tweaks

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Message-ID: <20160127161731-mutt-send-email-mst@redhat.com>
Date:	Wed, 27 Jan 2016 16:18:45 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Davidlohr Bueso <dave@...olabs.net>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Davidlohr Bueso <dbueso@...e.de>,
	virtualization <virtualization@...ts.linux-foundation.org>,
	Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH v2 0/3] x86: faster mb()+other barrier.h tweaks

On Wed, Jan 27, 2016 at 03:14:09PM +0100, Peter Zijlstra wrote:
> On Wed, Jan 27, 2016 at 04:07:56PM +0200, Michael S. Tsirkin wrote:
> > mwait_idle is the only one that calls smp_mb and not mb()
> > I couldn't figure out why - original patches did mb()
> > there.
> 
> That probably wants changing. That said, running UP kernels on affected
> hardware is 'unlikely' :-)

OK that's nice. After changing that one place, everyone calls
mb() around clflush so it should be safe to change smp_mb away
from mfence without breaking things.
I'm testing v4 that does this.

-- 
MST