From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754434AbbERWMh (ORCPT ); Mon, 18 May 2015 18:12:37 -0400 Received: from g9t5009.houston.hp.com ([15.240.92.67]:49554 "EHLO g9t5009.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750758AbbERWMe (ORCPT ); Mon, 18 May 2015 18:12:34 -0400 Message-ID: <1431985994.21526.12.camel@misato.fc.hp.com> Subject: Re: [PATCH v5 6/6] mtrr, mm, x86: Enhance MTRR checks for KVA huge page mapping From: Toshi Kani To: Borislav Petkov 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, mcgrof@suse.com Date: Mon, 18 May 2015 15:53:14 -0600 In-Reply-To: <20150518205123.GI23618@pd.tnic> References: <1431714237-880-1-git-send-email-toshi.kani@hp.com> <1431714237-880-7-git-send-email-toshi.kani@hp.com> <20150518133348.GA23618@pd.tnic> <1431969759.19889.5.camel@misato.fc.hp.com> <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> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4 (3.10.4-4.fc20) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2015-05-18 at 22:51 +0200, Borislav Petkov wrote: > On Mon, May 18, 2015 at 02:21:08PM -0600, Toshi Kani wrote: > > The caller is the one who makes the condition checks necessary to create > > a huge page mapping. > > How? It would go and change MTRRs configuration and ranges and their > memory types so that a huge mapping succeeds? > > Or go and try a different range? Try with a smaller page size. The callers, pud_set_huge() and pmd_set_huge(), check if the given range is safe with MTRRs for creating a huge page mapping. If not, they fail the request, which leads their callers, ioremap_pud_range() and ioremap_pmd_range(), to retry with a smaller page size, i.e. 1GB -> 2MB -> 4KB. 4KB may not have overlap with MTRRs (hence no checking is necessary), which will succeed as before. Thanks, -Toshi From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f173.google.com (mail-ob0-f173.google.com [209.85.214.173]) by kanga.kvack.org (Postfix) with ESMTP id A7FC96B0032 for ; Mon, 18 May 2015 18:12:35 -0400 (EDT) Received: by obcus9 with SMTP id us9so142957217obc.2 for ; Mon, 18 May 2015 15:12:35 -0700 (PDT) Received: from g9t5009.houston.hp.com (g9t5009.houston.hp.com. [15.240.92.67]) by mx.google.com with ESMTPS id g8si7203718oep.106.2015.05.18.15.12.34 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 18 May 2015 15:12:34 -0700 (PDT) Message-ID: <1431985994.21526.12.camel@misato.fc.hp.com> Subject: Re: [PATCH v5 6/6] mtrr, mm, x86: Enhance MTRR checks for KVA huge page mapping From: Toshi Kani Date: Mon, 18 May 2015 15:53:14 -0600 In-Reply-To: <20150518205123.GI23618@pd.tnic> References: <1431714237-880-1-git-send-email-toshi.kani@hp.com> <1431714237-880-7-git-send-email-toshi.kani@hp.com> <20150518133348.GA23618@pd.tnic> <1431969759.19889.5.camel@misato.fc.hp.com> <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> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Borislav Petkov 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, mcgrof@suse.com On Mon, 2015-05-18 at 22:51 +0200, Borislav Petkov wrote: > On Mon, May 18, 2015 at 02:21:08PM -0600, Toshi Kani wrote: > > The caller is the one who makes the condition checks necessary to create > > a huge page mapping. > > How? It would go and change MTRRs configuration and ranges and their > memory types so that a huge mapping succeeds? > > Or go and try a different range? Try with a smaller page size. The callers, pud_set_huge() and pmd_set_huge(), check if the given range is safe with MTRRs for creating a huge page mapping. If not, they fail the request, which leads their callers, ioremap_pud_range() and ioremap_pmd_range(), to retry with a smaller page size, i.e. 1GB -> 2MB -> 4KB. 4KB may not have overlap with MTRRs (hence no checking is necessary), which will succeed as before. Thanks, -Toshi -- 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