From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754171AbbETPBX (ORCPT ); Wed, 20 May 2015 11:01:23 -0400 Received: from mail-wg0-f51.google.com ([74.125.82.51]:35009 "EHLO mail-wg0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752558AbbETPBT (ORCPT ); Wed, 20 May 2015 11:01:19 -0400 Date: Wed, 20 May 2015 17:01:14 +0200 From: Ingo Molnar To: Toshi Kani Cc: Borislav Petkov , 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, mcgrof@suse.com Subject: Re: [PATCH v5 6/6] mtrr, mm, x86: Enhance MTRR checks for KVA huge page mapping Message-ID: <20150520150114.GA19161@gmail.com> References: <20150518190150.GC23618@pd.tnic> <1431977519.20569.15.camel@misato.fc.hp.com> <20150518200114.GE23618@pd.tnic> <1431980468.21019.11.camel@misato.fc.hp.com> <20150518205123.GI23618@pd.tnic> <1431985994.21526.12.camel@misato.fc.hp.com> <20150519114437.GF4641@pd.tnic> <20150519132307.GG4641@pd.tnic> <20150520115509.GA3489@gmail.com> <1432132451.700.4.camel@misato.fc.hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1432132451.700.4.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 * Toshi Kani wrote: > On Wed, 2015-05-20 at 13:55 +0200, Ingo Molnar wrote: > > * Borislav Petkov wrote: > > > > > --- a/arch/x86/mm/pgtable.c > > > +++ b/arch/x86/mm/pgtable.c > > > @@ -566,19 +566,28 @@ void native_set_fixmap(enum fixed_addresses idx, phys_addr_t phys, > > > /** > > > * pud_set_huge - setup kernel PUD mapping > > > * > > > - * MTRR can override PAT memory types with 4KiB granularity. Therefore, > > > - * this function does not set up a huge page when the range is covered > > > - * by a non-WB type of MTRR. MTRR_TYPE_INVALID indicates that MTRR are > > > - * disabled. > > > + * MTRRs can override PAT memory types with 4KiB granularity. Therefore, this > > > + * function sets up a huge page only if any of the following conditions are met: > > > + * > > > + * - MTRRs are disabled, or > > > + * > > > + * - MTRRs are enabled and the range is completely covered by a single MTRR, or > > > + * > > > + * - MTRRs are enabled and the range is not completely covered by a single MTRR > > > + * but the memory type of the range is WB, even if covered by multiple MTRRs. > > > + * > > > + * Callers should try to decrease page size (1GB -> 2MB -> 4K) if the bigger > > > + * page mapping attempt fails. > > > > This comment should explain why it's ok in the WB case. > > > > Also, the phrase 'the memory type of the range' is ambiguous: it might > > mean the partial MTRR's, or the memory type specified via PAT by the > > huge-pmd entry. > > Agreed. How about this sentence? > > - MTRRs are enabled and the corresponding MTRR memory type is WB, which > has no effect to the requested PAT memory type. s/effect to/effect on sounds good otherwise! Btw., if WB MTRR entries can never have an effect on Linux PAT specified attributes, why do we allow them to be created? I don't think we ever call into real mode for this to matter? Thanks, Ingo From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f53.google.com (mail-wg0-f53.google.com [74.125.82.53]) by kanga.kvack.org (Postfix) with ESMTP id 361DC6B0127 for ; Wed, 20 May 2015 11:01:20 -0400 (EDT) Received: by wgbgq6 with SMTP id gq6so56001217wgb.3 for ; Wed, 20 May 2015 08:01:19 -0700 (PDT) Received: from mail-wi0-x229.google.com (mail-wi0-x229.google.com. [2a00:1450:400c:c05::229]) by mx.google.com with ESMTPS id v3si1128512wix.97.2015.05.20.08.01.18 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 20 May 2015 08:01:19 -0700 (PDT) Received: by wicmx19 with SMTP id mx19so158265771wic.0 for ; Wed, 20 May 2015 08:01:18 -0700 (PDT) Date: Wed, 20 May 2015 17:01:14 +0200 From: Ingo Molnar Subject: Re: [PATCH v5 6/6] mtrr, mm, x86: Enhance MTRR checks for KVA huge page mapping Message-ID: <20150520150114.GA19161@gmail.com> References: <20150518190150.GC23618@pd.tnic> <1431977519.20569.15.camel@misato.fc.hp.com> <20150518200114.GE23618@pd.tnic> <1431980468.21019.11.camel@misato.fc.hp.com> <20150518205123.GI23618@pd.tnic> <1431985994.21526.12.camel@misato.fc.hp.com> <20150519114437.GF4641@pd.tnic> <20150519132307.GG4641@pd.tnic> <20150520115509.GA3489@gmail.com> <1432132451.700.4.camel@misato.fc.hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1432132451.700.4.camel@misato.fc.hp.com> Sender: owner-linux-mm@kvack.org List-ID: To: Toshi Kani Cc: Borislav Petkov , 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, mcgrof@suse.com * Toshi Kani wrote: > On Wed, 2015-05-20 at 13:55 +0200, Ingo Molnar wrote: > > * Borislav Petkov wrote: > > > > > --- a/arch/x86/mm/pgtable.c > > > +++ b/arch/x86/mm/pgtable.c > > > @@ -566,19 +566,28 @@ void native_set_fixmap(enum fixed_addresses idx, phys_addr_t phys, > > > /** > > > * pud_set_huge - setup kernel PUD mapping > > > * > > > - * MTRR can override PAT memory types with 4KiB granularity. Therefore, > > > - * this function does not set up a huge page when the range is covered > > > - * by a non-WB type of MTRR. MTRR_TYPE_INVALID indicates that MTRR are > > > - * disabled. > > > + * MTRRs can override PAT memory types with 4KiB granularity. Therefore, this > > > + * function sets up a huge page only if any of the following conditions are met: > > > + * > > > + * - MTRRs are disabled, or > > > + * > > > + * - MTRRs are enabled and the range is completely covered by a single MTRR, or > > > + * > > > + * - MTRRs are enabled and the range is not completely covered by a single MTRR > > > + * but the memory type of the range is WB, even if covered by multiple MTRRs. > > > + * > > > + * Callers should try to decrease page size (1GB -> 2MB -> 4K) if the bigger > > > + * page mapping attempt fails. > > > > This comment should explain why it's ok in the WB case. > > > > Also, the phrase 'the memory type of the range' is ambiguous: it might > > mean the partial MTRR's, or the memory type specified via PAT by the > > huge-pmd entry. > > Agreed. How about this sentence? > > - MTRRs are enabled and the corresponding MTRR memory type is WB, which > has no effect to the requested PAT memory type. s/effect to/effect on sounds good otherwise! Btw., if WB MTRR entries can never have an effect on Linux PAT specified attributes, why do we allow them to be created? I don't think we ever call into real mode for this to matter? Thanks, Ingo -- 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