From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753599AbbELQby (ORCPT ); Tue, 12 May 2015 12:31:54 -0400 Received: from mail.skyhub.de ([78.46.96.112]:54355 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753140AbbELQbw (ORCPT ); Tue, 12 May 2015 12:31:52 -0400 Date: Tue, 12 May 2015 18:31:48 +0200 From: Borislav Petkov To: Toshi Kani Cc: akpm@linux-foundation.org, hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com, linux-mm@kvack.org, x86@kernel.org, linux-kernel@vger.kernel.org, dave.hansen@intel.com, Elliott@hp.com, pebolle@tiscali.nl Subject: Re: [PATCH v4 7/7] mtrr, mm, x86: Enhance MTRR checks for KVA huge page mapping Message-ID: <20150512163148.GH3497@pd.tnic> References: <1427234921-19737-1-git-send-email-toshi.kani@hp.com> <1427234921-19737-8-git-send-email-toshi.kani@hp.com> <20150509090810.GB4452@pd.tnic> <1431372316.23761.440.camel@misato.fc.hp.com> <20150511201827.GI15636@pd.tnic> <1431376726.23761.471.camel@misato.fc.hp.com> <20150511214244.GK15636@pd.tnic> <1431382179.24419.12.camel@misato.fc.hp.com> <20150512072809.GA3497@pd.tnic> <1431441030.24419.81.camel@misato.fc.hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1431441030.24419.81.camel@misato.fc.hp.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 On Tue, May 12, 2015 at 08:30:30AM -0600, Toshi Kani wrote: > MTRR_TYPE_INVALID means MTRRs disabled. So, the caller checking with > this value is the same as checking with mtrr_enabled() you suggested. So then you don't have to set *uniform = 1 on entry to mtrr_type_lookup(). And change the retval test if ((!uniform) && (mtrr != MTRR_TYPE_WRBACK)) to if ((mtrr != MTRR_TYPE_INVALID) && (!uniform) && (mtrr != MTRR_TYPE_WRBACK)) You can put the MTRR_TYPE_INVALID first so that it shortcuts. You need the distinction between MTRRs *disabled* and an MTRR region being {non-,}uniform. If MTRRs are disabled, uniform doesn't *mean* *anything* because it is undefined. When MTRRs are disabled, the range is *not* covered by MTRRs because, well, them MTRRs are disabled. And it might be fine for *your* use case to set *uniform even when MTRRs are disabled but it might matter in the future. So we better design it correct from the beginning. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f169.google.com (mail-wi0-f169.google.com [209.85.212.169]) by kanga.kvack.org (Postfix) with ESMTP id 61E276B0038 for ; Tue, 12 May 2015 12:31:53 -0400 (EDT) Received: by wizk4 with SMTP id k4so161930042wiz.1 for ; Tue, 12 May 2015 09:31:52 -0700 (PDT) Received: from mail.skyhub.de (mail.skyhub.de. [2a01:4f8:120:8448::d00d]) by mx.google.com with ESMTP id g14si28305821wjz.39.2015.05.12.09.31.51 for ; Tue, 12 May 2015 09:31:51 -0700 (PDT) Date: Tue, 12 May 2015 18:31:48 +0200 From: Borislav Petkov Subject: Re: [PATCH v4 7/7] mtrr, mm, x86: Enhance MTRR checks for KVA huge page mapping Message-ID: <20150512163148.GH3497@pd.tnic> References: <1427234921-19737-1-git-send-email-toshi.kani@hp.com> <1427234921-19737-8-git-send-email-toshi.kani@hp.com> <20150509090810.GB4452@pd.tnic> <1431372316.23761.440.camel@misato.fc.hp.com> <20150511201827.GI15636@pd.tnic> <1431376726.23761.471.camel@misato.fc.hp.com> <20150511214244.GK15636@pd.tnic> <1431382179.24419.12.camel@misato.fc.hp.com> <20150512072809.GA3497@pd.tnic> <1431441030.24419.81.camel@misato.fc.hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1431441030.24419.81.camel@misato.fc.hp.com> Sender: owner-linux-mm@kvack.org List-ID: To: Toshi Kani Cc: akpm@linux-foundation.org, hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com, linux-mm@kvack.org, x86@kernel.org, linux-kernel@vger.kernel.org, dave.hansen@intel.com, Elliott@hp.com, pebolle@tiscali.nl On Tue, May 12, 2015 at 08:30:30AM -0600, Toshi Kani wrote: > MTRR_TYPE_INVALID means MTRRs disabled. So, the caller checking with > this value is the same as checking with mtrr_enabled() you suggested. So then you don't have to set *uniform = 1 on entry to mtrr_type_lookup(). And change the retval test if ((!uniform) && (mtrr != MTRR_TYPE_WRBACK)) to if ((mtrr != MTRR_TYPE_INVALID) && (!uniform) && (mtrr != MTRR_TYPE_WRBACK)) You can put the MTRR_TYPE_INVALID first so that it shortcuts. You need the distinction between MTRRs *disabled* and an MTRR region being {non-,}uniform. If MTRRs are disabled, uniform doesn't *mean* *anything* because it is undefined. When MTRRs are disabled, the range is *not* covered by MTRRs because, well, them MTRRs are disabled. And it might be fine for *your* use case to set *uniform even when MTRRs are disabled but it might matter in the future. So we better design it correct from the beginning. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org