From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753298Ab2GXKwa (ORCPT ); Tue, 24 Jul 2012 06:52:30 -0400 Received: from comal.ext.ti.com ([198.47.26.152]:58715 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753091Ab2GXKw3 (ORCPT ); Tue, 24 Jul 2012 06:52:29 -0400 Message-ID: <500E7E5E.1030005@ti.com> Date: Tue, 24 Jul 2012 06:52:14 -0400 From: Cyril Chemparathy User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:14.0) Gecko/20120713 Thunderbird/14.0 MIME-Version: 1.0 To: Catalin Marinas CC: "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "nico@linaro.org" , Will Deacon , Vitaly Andrianov Subject: Re: [RFC 02/23] ARM: LPAE: use signed arithmetic for mask definitions References: <1343092165-9470-1-git-send-email-cyril@ti.com> <1343092165-9470-3-git-send-email-cyril@ti.com> <20120724100511.GE20132@arm.com> In-Reply-To: <20120724100511.GE20132@arm.com> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/24/2012 6:05 AM, Catalin Marinas wrote: > On Tue, Jul 24, 2012 at 02:09:04AM +0100, Cyril Chemparathy wrote: >> This patch applies to PAGE_MASK, PMD_MASK, and PGDIR_MASK, where forcing >> unsigned long math truncates the mask at the 32-bits. This clearly does bad >> things on PAE systems. >> >> This patch fixes this problem by defining these masks as signed quantities. >> We then rely on sign extension to do the right thing. >> >> Signed-off-by: Cyril Chemparathy >> Signed-off-by: Vitaly Andrianov >> --- >> arch/arm/include/asm/page.h | 7 ++++++- >> arch/arm/include/asm/pgtable-3level.h | 6 +++--- >> 2 files changed, 9 insertions(+), 4 deletions(-) >> >> diff --git a/arch/arm/include/asm/page.h b/arch/arm/include/asm/page.h >> index ecf9019..1c810d2 100644 >> --- a/arch/arm/include/asm/page.h >> +++ b/arch/arm/include/asm/page.h >> @@ -13,7 +13,12 @@ >> /* PAGE_SHIFT determines the page size */ >> #define PAGE_SHIFT 12 >> #define PAGE_SIZE (_AC(1,UL) << PAGE_SHIFT) >> -#define PAGE_MASK (~(PAGE_SIZE-1)) >> + >> +/* >> + * We do not use PAGE_SIZE in the following because we rely on sign >> + * extension to appropriately extend upper bits for PAE systems >> + */ >> +#define PAGE_MASK (~((1 << PAGE_SHIFT) - 1)) > > Would it work if we use a 1ULL here and avoid the sign trick? I'm > worried about some context where this would lose the sign. We could have > an #ifdef here while the PGDIR/PMD masks are in a separate file already. > Sure, I will modify accordingly in the next version. -- Thanks - Cyril From mboxrd@z Thu Jan 1 00:00:00 1970 From: cyril@ti.com (Cyril Chemparathy) Date: Tue, 24 Jul 2012 06:52:14 -0400 Subject: [RFC 02/23] ARM: LPAE: use signed arithmetic for mask definitions In-Reply-To: <20120724100511.GE20132@arm.com> References: <1343092165-9470-1-git-send-email-cyril@ti.com> <1343092165-9470-3-git-send-email-cyril@ti.com> <20120724100511.GE20132@arm.com> Message-ID: <500E7E5E.1030005@ti.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 7/24/2012 6:05 AM, Catalin Marinas wrote: > On Tue, Jul 24, 2012 at 02:09:04AM +0100, Cyril Chemparathy wrote: >> This patch applies to PAGE_MASK, PMD_MASK, and PGDIR_MASK, where forcing >> unsigned long math truncates the mask at the 32-bits. This clearly does bad >> things on PAE systems. >> >> This patch fixes this problem by defining these masks as signed quantities. >> We then rely on sign extension to do the right thing. >> >> Signed-off-by: Cyril Chemparathy >> Signed-off-by: Vitaly Andrianov >> --- >> arch/arm/include/asm/page.h | 7 ++++++- >> arch/arm/include/asm/pgtable-3level.h | 6 +++--- >> 2 files changed, 9 insertions(+), 4 deletions(-) >> >> diff --git a/arch/arm/include/asm/page.h b/arch/arm/include/asm/page.h >> index ecf9019..1c810d2 100644 >> --- a/arch/arm/include/asm/page.h >> +++ b/arch/arm/include/asm/page.h >> @@ -13,7 +13,12 @@ >> /* PAGE_SHIFT determines the page size */ >> #define PAGE_SHIFT 12 >> #define PAGE_SIZE (_AC(1,UL) << PAGE_SHIFT) >> -#define PAGE_MASK (~(PAGE_SIZE-1)) >> + >> +/* >> + * We do not use PAGE_SIZE in the following because we rely on sign >> + * extension to appropriately extend upper bits for PAE systems >> + */ >> +#define PAGE_MASK (~((1 << PAGE_SHIFT) - 1)) > > Would it work if we use a 1ULL here and avoid the sign trick? I'm > worried about some context where this would lose the sign. We could have > an #ifdef here while the PGDIR/PMD masks are in a separate file already. > Sure, I will modify accordingly in the next version. -- Thanks - Cyril