From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f170.google.com (mail-io0-f170.google.com [209.85.223.170]) by kanga.kvack.org (Postfix) with ESMTP id 2ACBF6B0038 for ; Wed, 25 Nov 2015 07:06:10 -0500 (EST) Received: by iouu10 with SMTP id u10so52222129iou.0 for ; Wed, 25 Nov 2015 04:06:10 -0800 (PST) Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id 69si20879128iod.65.2015.11.25.04.06.09 for ; Wed, 25 Nov 2015 04:06:09 -0800 (PST) Date: Wed, 25 Nov 2015 12:06:01 +0000 From: Catalin Marinas Subject: Re: [PATCH v3 3/4] arm64: mm: support ARCH_MMAP_RND_BITS. Message-ID: <20151125120601.GC3109@e104818-lin.cambridge.arm.com> References: <1447888808-31571-1-git-send-email-dcashman@android.com> <1447888808-31571-2-git-send-email-dcashman@android.com> <1447888808-31571-3-git-send-email-dcashman@android.com> <1447888808-31571-4-git-send-email-dcashman@android.com> <20151123150459.GD4236@arm.com> <56536114.1020305@android.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56536114.1020305@android.com> Sender: owner-linux-mm@kvack.org List-ID: To: Daniel Cashman Cc: Will Deacon , dcashman@google.com, linux-doc@vger.kernel.org, linux-mm@kvack.org, hpa@zytor.com, mingo@kernel.org, aarcange@redhat.com, linux@arm.linux.org.uk, corbet@lwn.net, xypron.glpk@gmx.de, x86@kernel.org, hecmargi@upv.es, mgorman@suse.de, rientjes@google.com, bp@suse.de, nnk@google.com, dzickus@redhat.com, keescook@chromium.org, jpoimboe@redhat.com, tglx@linutronix.de, n-horiguchi@ah.jp.nec.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, salyzyn@android.com, ebiederm@xmission.com, jeffv@google.com, akpm@linux-foundation.org, kirill.shutemov@linux.intel.com On Mon, Nov 23, 2015 at 10:55:16AM -0800, Daniel Cashman wrote: > On 11/23/2015 07:04 AM, Will Deacon wrote: > > On Wed, Nov 18, 2015 at 03:20:07PM -0800, Daniel Cashman wrote: > >> +config ARCH_MMAP_RND_BITS_MAX > >> + default 20 if ARM64_64K_PAGES && ARCH_VA_BITS=39 Where is ARCH_VA_BITS defined? We only have options like ARM64_VA_BITS_39. BTW, we no longer allow the 64K pages and 39-bit VA combination. > >> + default 24 if ARCH_VA_BITS=39 > >> + default 23 if ARM64_64K_PAGES && ARCH_VA_BITS=42 > >> + default 27 if ARCH_VA_BITS=42 > >> + default 29 if ARM64_64K_PAGES && ARCH_VA_BITS=48 > >> + default 33 if ARCH_VA_BITS=48 > >> + default 15 if ARM64_64K_PAGES > >> + default 19 > >> + > >> +config ARCH_MMAP_RND_COMPAT_BITS_MIN > >> + default 7 if ARM64_64K_PAGES > >> + default 11 > > > > FYI: we now support 16k pages too, so this might need updating. It would > > be much nicer if this was somehow computed rather than have the results > > all open-coded like this. > > Yes, I ideally wanted this to be calculated based on the different page > options and VA_BITS (which itself has a similar stanza), but I don't > know how to do that/if it is currently supported in Kconfig. This would > be even more desirable with the addition of 16K_PAGES, as with this > setup we have a combinatorial problem. For KASan, we ended up calculating KASAN_SHADOW_OFFSET in arch/arm64/Makefile. What would the formula be for the above ARCH_MMAP_RND_BITS_MAX? -- Catalin -- 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