Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759392Ab0GPW26 (ORCPT ); Fri, 16 Jul 2010 18:28:58 -0400 Received: from terminus.zytor.com ([198.137.202.10]:33933 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759360Ab0GPW25 (ORCPT ); Fri, 16 Jul 2010 18:28:57 -0400 Message-ID: <4C40DD11.4020803@zytor.com> Date: Fri, 16 Jul 2010 15:28:33 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.10) Gecko/20100621 Fedora/3.0.5-1.fc13 Thunderbird/3.0.5 MIME-Version: 1.0 To: Borislav Petkov CC: Michal Schmidt , "linux-kernel@vger.kernel.org" , Thomas Gleixner , "Herrmann3, Andreas" , Shaohua Li , Ingo Molnar Subject: Re: [PATCH 1/2] x86: fix keeping track of AMD C1E References: <20100713185816.2866.17837.stgit@localhost.localdomain> <20100713185957.2866.50995.stgit@localhost.localdomain> <20100714160704.GA10473@kryptos.osrc.amd.com> <20100714232201.00433aa9@hammerfall> <20100714233102.0f64614b@hammerfall> <4C3FDF43.6030203@zytor.com> <20100716063952.GB27546@aftab> <4C3F8418.5020803@zytor.com> <20100716072244.GA27954@aftab> <4C408298.8060004@zytor.com> <20100716162517.GF28902@aftab> In-Reply-To: <20100716162517.GF28902@aftab> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1255 Lines: 29 On 07/16/2010 09:25 AM, Borislav Petkov wrote: > > I don't see the need for two things denoting C1E for the very simple > reason: when C1E gets enabled on a machine, one of the bits gets set in > the MSR on each core simultaneously. So if one core sees one of the bits > set, all the remaining cores are seeing them too. The first core that > sees one of the bits in the MSR, sets c1e_detected. > > So next time any core does cpu_idle() => c1e_idle(), it switches to > timer broadcast on it since it might go into C1E if all the others > follow. > > Frankly, I can't think of a case where we'd need to two things - I > could be missing something. But this workaround is a couple of years > old, maybe Thomas might give us more insight into whether there's a > particular reason for the cpuid flag and the c1e_detected variable. > Thomas? > I'm not saying there should be two things (and that's clearly wrong no matter what), but rather it's not clear to me that the one thing should be a variable. -hpa -- 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/