From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751699AbbLCRrQ (ORCPT ); Thu, 3 Dec 2015 12:47:16 -0500 Received: from foss.arm.com ([217.140.101.70]:50459 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751159AbbLCRrN (ORCPT ); Thu, 3 Dec 2015 12:47:13 -0500 Date: Thu, 3 Dec 2015 17:47:08 +0000 From: Catalin Marinas To: Yury Norov Cc: Arnd Bergmann , pinskia@gmail.com, Prasun.Kapoor@caviumnetworks.com, Nathan_Lynch@mentor.com, linux-kernel@vger.kernel.org, agraf@suse.de, klimov.linux@gmail.com, broonie@kernel.org, jan.dakinevich@gmail.com, joseph@codesourcery.com, ddaney.cavm@gmail.com, schwab@suse.de, bamvor.zhangjian@huawei.com, philipp.tomsich@theobroma-systems.com, andrey.konovalov@linaro.org, linux-arm-kernel@lists.infradead.org, christoph.muellner@theobroma-systems.com Subject: Re: [PATCH v6 14/19] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it Message-ID: <20151203174708.GO10747@e104818-lin.cambridge.arm.com> References: <1447795019-30176-1-git-send-email-ynorov@caviumnetworks.com> <1447795019-30176-15-git-send-email-ynorov@caviumnetworks.com> <3754277.KmO9Nk3XLD@wuerfel> <20151201212904.GA14442@yury-N73SV> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151201212904.GA14442@yury-N73SV> 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 Wed, Dec 02, 2015 at 12:29:04AM +0300, Yury Norov wrote: > My question. Why aarch64 defines COMPAT_SHMLBA as 0x4000? This was done to match the arch/arm value of 4 * 4K. The historical 32-bit reason for 4 pages is to cope with aliasing VIPT caches (see https://git.kernel.org/cgit/linux/kernel/git/tglx/history.git/commit?id=4197692eef113eeb8e3e413cc70993a5e667e5b8) > If there's > no specific reason for it, it looks like a bug, and we should > define it like in arch/arm: > #define SHMLBA (4 * PAGE_SIZE) /* attach addr a multiple of this */ I guess you meant COMPAT_SHMLBA. I'm not sure there is much value in keeping 4*PAGE_SIZE for larger page sizes but I agree that the current 16K value doesn't work well with 64K pages. -- Catalin From mboxrd@z Thu Jan 1 00:00:00 1970 From: catalin.marinas@arm.com (Catalin Marinas) Date: Thu, 3 Dec 2015 17:47:08 +0000 Subject: [PATCH v6 14/19] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it In-Reply-To: <20151201212904.GA14442@yury-N73SV> References: <1447795019-30176-1-git-send-email-ynorov@caviumnetworks.com> <1447795019-30176-15-git-send-email-ynorov@caviumnetworks.com> <3754277.KmO9Nk3XLD@wuerfel> <20151201212904.GA14442@yury-N73SV> Message-ID: <20151203174708.GO10747@e104818-lin.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Dec 02, 2015 at 12:29:04AM +0300, Yury Norov wrote: > My question. Why aarch64 defines COMPAT_SHMLBA as 0x4000? This was done to match the arch/arm value of 4 * 4K. The historical 32-bit reason for 4 pages is to cope with aliasing VIPT caches (see https://git.kernel.org/cgit/linux/kernel/git/tglx/history.git/commit?id=4197692eef113eeb8e3e413cc70993a5e667e5b8) > If there's > no specific reason for it, it looks like a bug, and we should > define it like in arch/arm: > #define SHMLBA (4 * PAGE_SIZE) /* attach addr a multiple of this */ I guess you meant COMPAT_SHMLBA. I'm not sure there is much value in keeping 4*PAGE_SIZE for larger page sizes but I agree that the current 16K value doesn't work well with 64K pages. -- Catalin