From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-we0-f169.google.com (mail-we0-f169.google.com [74.125.82.169]) by kanga.kvack.org (Postfix) with ESMTP id 495FA6B006E for ; Tue, 24 Feb 2015 03:09:33 -0500 (EST) Received: by wesw62 with SMTP id w62so23468956wes.9 for ; Tue, 24 Feb 2015 00:09:32 -0800 (PST) Received: from mail-wi0-x234.google.com (mail-wi0-x234.google.com. [2a00:1450:400c:c05::234]) by mx.google.com with ESMTPS id p8si66155556wjy.134.2015.02.24.00.09.31 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 24 Feb 2015 00:09:31 -0800 (PST) Received: by mail-wi0-f180.google.com with SMTP id h11so23118386wiw.1 for ; Tue, 24 Feb 2015 00:09:30 -0800 (PST) Date: Tue, 24 Feb 2015 09:09:27 +0100 From: Ingo Molnar Subject: Re: [PATCH v2 0/7] Kernel huge I/O mapping support Message-ID: <20150224080927.GB19069@gmail.com> References: <1423521935-17454-1-git-send-email-toshi.kani@hp.com> <20150223122224.c55554325cc4dadeca067234@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150223122224.c55554325cc4dadeca067234@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Toshi Kani , hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com, arnd@arndb.de, linux-mm@kvack.org, x86@kernel.org, linux-kernel@vger.kernel.org, Elliott@hp.com * Andrew Morton wrote: > > > Oh. We don't do any checking at all. We're just telling > userspace programmers "don't do that". hrm. What are > your thoughts on adding the overlap checks to the kernel? I have requested such sanity checking in previous review as well, it has to be made fool-proof for this optimization to be usable. Another alternative would be to make this not a transparent optimization, but a separate API: ioremap_hugepage() or so. The devices and drivers dealing with GBs of remapped pages is still relatively low, so they could make explicit use of the API and opt in to it. What I was arguing against was to make it a CONFIG_ option: that achieves very little in practice, such APIs should be uniformly available. 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