From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S968147Ab0B0Jxd (ORCPT ); Sat, 27 Feb 2010 04:53:33 -0500 Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:38624 "EHLO sunset.davemloft.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S968133Ab0B0Jxc (ORCPT ); Sat, 27 Feb 2010 04:53:32 -0500 Date: Sat, 27 Feb 2010 01:53:50 -0800 (PST) Message-Id: <20100227.015350.71138134.davem@davemloft.net> To: hancockrwd@gmail.com Cc: bzolnier@gmail.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-usb@vger.kernel.org Subject: Re: [RFC PATCH] fix problems with NETIF_F_HIGHDMA in networking drivers From: David Miller In-Reply-To: <51f3faa71002261908y7cfa62eeicb3e56d5c920887a@mail.gmail.com> References: <51f3faa71002260646r705891e8tdbab1f6faeeb4b81@mail.gmail.com> <201002261625.24523.bzolnier@gmail.com> <51f3faa71002261908y7cfa62eeicb3e56d5c920887a@mail.gmail.com> X-Mailer: Mew version 6.3 on Emacs 23.1 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Robert Hancock Date: Fri, 26 Feb 2010 21:08:04 -0600 > That seems like a reasonable approach to me. Only question is how to > implement the check for DMA_64BIT. Can we just check page_to_phys on > each of the pages in the skb to see if it's > 0xffffffff ? Are there > any architectures where it's more complicated than that? On almost every platform it's "more complicated than that". This is the whole issue. What matters is the final DMA address and since we have IOMMUs and the like, it is absolutely not tenable to solve this by checking physical address attributes.