From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx158.postini.com [74.125.245.158]) by kanga.kvack.org (Postfix) with SMTP id 199446B004D for ; Mon, 30 Jan 2012 14:19:44 -0500 (EST) Received: by mail-wi0-f177.google.com with SMTP id o1so4702932wic.8 for ; Mon, 30 Jan 2012 11:19:38 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20120128192553.GA16231@obsidianresearch.com> References: <1327557574-6125-1-git-send-email-roland@kernel.org> <20120128192553.GA16231@obsidianresearch.com> From: Roland Dreier Date: Mon, 30 Jan 2012 11:19:18 -0800 Message-ID: Subject: Re: [PATCH/RFC G-U-P experts] IB/umem: Modernize our get_user_pages() parameters Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Jason Gunthorpe Cc: Hugh Dickins , linux-rdma@vger.kernel.org, Andrea Arcangeli , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Sat, Jan 28, 2012 at 11:25 AM, Jason Gunthorpe wrote: > I know accessing system memory (eg obtained via mmap on > /sys/bus/pci/devices/0000:00:02.0/resource0) has been asked for in the > past, and IIRC, the problem was that some of the common code, (GUP?) > errored on these maps. I don't know if Roland's case is similar. I think the problem there is that this is done via remap_pfn_range() or similar, and the mapping has no underlying pages at all. So we would need a new interface that gives us different information for such cases. This is quite a bit trickier since I don't think the DMA API even has a way to express getting a "device A" bus address for some memory that is in a BAR for "device B". So I'm not trying to address this case (yet). First I'd like to deal with as many flavors of page-backed mappings as I can. - R. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org