From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932410AbaJ2Kmg (ORCPT ); Wed, 29 Oct 2014 06:42:36 -0400 Received: from mail-wi0-f182.google.com ([209.85.212.182]:61856 "EHLO mail-wi0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932168AbaJ2Kme (ORCPT ); Wed, 29 Oct 2014 06:42:34 -0400 Date: Wed, 29 Oct 2014 11:36:05 +0100 From: Ingo Molnar To: Juergen Gross Cc: Thomas Gleixner , hpa@zytor.com, x86@kernel.org, mingo@redhat.com, stefan.bader@canonical.com, linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, konrad.wilk@oracle.com, ville.syrjala@linux.intel.com, david.vrabel@citrix.com, jbeulich@suse.com, toshi.kani@hp.com Subject: Re: [PATCH V4 1/3] x86: Make page cache mode a real type Message-ID: <20141029103605.GA11648@gmail.com> References: <1414392513-24645-1-git-send-email-jgross@suse.com> <1414392513-24645-2-git-send-email-jgross@suse.com> <20141029102859.GA11260@gmail.com> <5450C2F3.40400@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5450C2F3.40400@suse.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Juergen Gross wrote: > On 10/29/2014 11:28 AM, Ingo Molnar wrote: > > > >* Thomas Gleixner wrote: > > > >>On Mon, 27 Oct 2014, Juergen Gross wrote: > >>>At the moment there are a lot of places that handle setting or getting > >>>the page cache mode by treating the pgprot bits equal to the cache mode. > >>>This is only true because there are a lot of assumptions about the setup > >>>of the PAT MSR. Otherwise the cache type needs to get translated into > >>>pgprot bits and vice versa. > >>> > >>>This patch tries to prepare for that by introducing a separate type > >>>for the cache mode and adding functions to translate between those and > >>>pgprot values. > >>> > >>>To avoid too much performance penalty the translation between cache mode > >>>and pgprot values is done via tables which contain the relevant > >>>information. Write-back cache mode is hard-wired to be 0, all other > >>>modes are configurable via those tables. For large pages there are > >>>translation functions as the PAT bit is located at different positions > >>>in the ptes of 4k and large pages. > >> > >>I'm fine with the approach itself. Though I wish you had split this > >>patch in several sanely to review pieces. > >> > >> - Introduce enums, helper functions etc. which basically reflect > >> the state of today > >> > >> - Change the usage sites to use the enums and helpers > >> > >> - Convert the enum/helper implementation to the new scheme > >> > >> - Split out the printk change > >> > >> ... > > > >That absolutely has to be done, should any of this introduce > >regressions. The diffstat: > > > > 18 files changed, 344 insertions(+), 212 deletions(-) > > > >is _way_ too large. > > Okay, will do. Thanks! Ingo