Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756536Ab1EJPXM (ORCPT ); Tue, 10 May 2011 11:23:12 -0400 Received: from cantor2.suse.de ([195.135.220.15]:47764 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751700Ab1EJPXL (ORCPT ); Tue, 10 May 2011 11:23:11 -0400 Date: Tue, 10 May 2011 08:13:05 -0700 From: Greg KH To: Borislav Petkov Cc: Ben Hutchings , Borislav Petkov , "Rosenfeld, Hans" , "linux-kernel@vger.kernel.org" , "stable@kernel.org" , "akpm@linux-foundation.org" , "H. Peter Anvin" , "torvalds@linux-foundation.org" , "stable-review@kernel.org" , "alan@lxorguk.ukuu.org.uk" , "Ostrovsky, Boris" Subject: Re: [Stable-review] [12/28] x86, cpu: Clean up AMD erratum 400 workaround Message-ID: <20110510151305.GA9824@suse.de> References: <20110420020128.GA27631@suse.de> <1303265862.3464.77.camel@localhost> <20110420031105.GA11945@suse.de> <1303274910.3464.95.camel@localhost> <20110420050617.GA16756@suse.de> <1303356555.3464.128.camel@localhost> <20110505225302.GC12316@suse.de> <20110506074120.GB21046@liondog.tnic> <1305032339.4065.276.camel@localhost> <20110510140219.GB16789@aftab> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110510140219.GB16789@aftab> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1660 Lines: 41 On Tue, May 10, 2011 at 04:02:19PM +0200, Borislav Petkov wrote: > On Tue, May 10, 2011 at 08:58:59AM -0400, Ben Hutchings wrote: > > I read that: > > > > " > > Support for Always Running APIC timer (ARAT) was introduced in > > commit db954b5898dd3ef3ef93f4144158ea8f97deb058. This feature > > allows us to avoid switching timers from LAPIC to something else > > (e.g. HPET) and go into timer broadcasts when entering deep > > C-states. > > > > AMD processors don't provide a CPUID bit for that feature but > > they also keep APIC timers running in deep C-states (except for > > cases when the processor is affected by erratum 400). Therefore > > we should set ARAT feature bit on AMD CPUs. > > " > > > > This implies that the HPET was previously used during deep C-states, and > > that all this erratum checking is about deciding whether the CPU has > > ARAT. So what bug is being fixed by using ARAT instead of the HPET? > > That's a good question, actually. The original upstream commit > b87cf80af3ba4b4c008b4face3c68d604e1715c6 wasn't tagged for stable and > Boris O. didn't send it to stable either, as I'm being told. > > Maybe Greg has an idea? I added it because it was needed to get another errata patch to apply properly, and I saw no reason not to apply other "quirks" like this to older kernels, right? Or should I not have done that? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/