From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f54.google.com (mail-wm0-f54.google.com [74.125.82.54]) by kanga.kvack.org (Postfix) with ESMTP id 95B0B6B0255 for ; Wed, 9 Dec 2015 08:55:47 -0500 (EST) Received: by wmuu63 with SMTP id u63so223421457wmu.0 for ; Wed, 09 Dec 2015 05:55:47 -0800 (PST) Received: from mail-wm0-f52.google.com (mail-wm0-f52.google.com. [74.125.82.52]) by mx.google.com with ESMTPS id k76si14309893wmg.99.2015.12.09.05.55.45 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 09 Dec 2015 05:55:46 -0800 (PST) Received: by wmec201 with SMTP id c201so74564693wme.1 for ; Wed, 09 Dec 2015 05:55:45 -0800 (PST) Date: Wed, 9 Dec 2015 14:55:44 +0100 From: Michal Hocko Subject: Re: m(un)map kmalloc buffers to userspace Message-ID: <20151209135544.GE30907@dhcp22.suse.cz> References: <5667128B.3080704@sigmadesigns.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5667128B.3080704@sigmadesigns.com> Sender: owner-linux-mm@kvack.org List-ID: To: Sebastian Frias Cc: linux-mm@kvack.org, Marc Gonzalez , linux-kernel@vger.kernel.org On Tue 08-12-15 18:25:31, Sebastian Frias wrote: > Hi, > > We are porting a driver from Linux 3.4.39+ to 4.1.13+, CPU is Cortex-A9. > > The driver maps kmalloc'ed memory to user space. This sounds like a terrible idea to me. Why don't you simply use the page allocator directly? Try to imagine what would happen if you mmaped a kmalloc with a size which is not page aligned? mmaped memory uses whole page granularity. -- Michal Hocko SUSE Labs -- 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