From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751885AbcCOVJf (ORCPT ); Tue, 15 Mar 2016 17:09:35 -0400 Received: from g9t5009.houston.hp.com ([15.240.92.67]:40936 "EHLO g9t5009.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750926AbcCOVJd (ORCPT ); Tue, 15 Mar 2016 17:09:33 -0400 Message-ID: <1458079320.6393.376.camel@hpe.com> Subject: Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT table From: Toshi Kani To: Borislav Petkov Cc: "mingo@kernel.org" , "hpa@zytor.com" , "tglx@linutronix.de" , "mcgrof@suse.com" , "jgross@suse.com" , "paul.gortmaker@windriver.com" , "x86@kernel.org" , "linux-kernel@vger.kernel.org" Date: Tue, 15 Mar 2016 16:02:00 -0600 In-Reply-To: <20160315110005.GB4559@pd.tnic> References: <1457671546-13486-1-git-send-email-toshi.kani@hpe.com> <1457671546-13486-2-git-send-email-toshi.kani@hpe.com> <20160311091229.GA4347@pd.tnic> <1457713660.6393.55.camel@hpe.com> <20160311155439.GF4312@pd.tnic> <1457724504.6393.151.camel@hpe.com> <20160312115544.GA23410@pd.tnic> <1457991443.6393.290.camel@hpe.com> <20160315110005.GB4559@pd.tnic> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.18.4 (3.18.4-1.fc23) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2016-03-15 at 12:00 +0100, Borislav Petkov wrote: > On Mon, Mar 14, 2016 at 03:37:23PM -0600, Toshi Kani wrote: > > Your patch is a simplified version of mine.  So, yes, it fixes the > > Paul's issue, but it does not address other issues that my patchset > > also addressed.  In specific, I think your patch has the following > > issues. > > You couldnt've structured your reply better: remember how I split a > convoluted patch of yours already? A patch which was trying to do a > bunch of things in one go. > > The situation here is the same. You need to do *one* *logical* > *non-trivial* thing in a patch. If there's something else that needs to > be done, add it in a *separate* patch which explains why that new change > is needed. Got it! > > - pat_disable() is now callable from other modules. So, it needs to > > check with boot_cpu_done. We cannot disable PAT once it is initialized. > > That should be a separate patch which explains *why* the change is being > done. > > > - mtrr_bp_init() needs to check with mtrr_enabled() when it > > calls mtrr_pat_setup_bp(). Otherwise, PAT is left initialized on BSP > > only when MTRR is disabled by its MSR. In your patch, mtrr_bp_init() > > calls pat_setup() again, but it does not help since boot_cpu_done is > > set. > > The code which you carved out from get_mtrr_state() didn't check > mtrr_enabled() before. That needs to be another patch *again* with > explanations. > > > - When PAT is disabled in CPU feature, pat_bsp_init() calls > > pat_disable() and returns. However, it does not initialize a PAT table > > by calling pat_init_cache_modes(). > > Yet another patch. > > > - When CONFIG_MTRR is unset, it does not call pat_setup(). > > Aaaand... can you guess what I'm going to say here? > > I hope it is coming across as I intend it: please use my hunk to do a > single fix and then prepare all those changes above in separate patches > with explanations: Unfortunately, this single fix will break Xen.  So, I think we will need to make a few enhancements first before making the fix. > "Problem is A. We need to do B. I'm doing it/I'm doing C because." > > Ok? Yes, I will try to separate the patches to change one logical thing at a time.  Thanks, -Toshi