From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [PATCH 1/1] x86: replace cpu_up hard-coded mdelay with variable Date: Mon, 20 Apr 2015 19:45:44 +0200 Message-ID: <20150420174544.GA18931@gmail.com> References: <1429404795-23260-1-git-send-email-lenb@kernel.org> <87d69aab88c14d65ae1e7be55050d1b689b59b4b.1429402494.git.len.brown@intel.com> <20150420071306.GA14315@gmail.com> <1A7043D5F58CCB44A599DFD55ED4C94846861500@fmsmsx115.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-wi0-f174.google.com ([209.85.212.174]:34416 "EHLO mail-wi0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750771AbbDTRpu (ORCPT ); Mon, 20 Apr 2015 13:45:50 -0400 Content-Disposition: inline In-Reply-To: <1A7043D5F58CCB44A599DFD55ED4C94846861500@fmsmsx115.amr.corp.intel.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: "Brown, Len" Cc: Len Brown , "x86@kernel.org" , "linux-pm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Borislav Petkov , "H. Peter Anvin" , Thomas Gleixner * Brown, Len wrote: > > What's the cutoff for 'modern hardware' - which CPUs stopped requiring > > the delay? > > This is the topic of ongoing research, and I'm not ready to send > the patch setting a new default until I've heard back from a few more HW people. > > Every system I've tested appears to work with delay 0. > Were I to guess, I'd venture that every > system that runs an X86_64 kernel might count as "modern" -- even > the 2005 AMD Turion laptop I've got in the bone pile. Could we use the apic version as a cutoff perhaps? It would be nice to 'automatically' include modern 32-bit x86 systems as well. Any failure here would be relatively easy to bisect to, so we might as well guess a bit and refine the quirk condition if needed? Thanks, Ingo