From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757349Ab0JVApx (ORCPT ); Thu, 21 Oct 2010 20:45:53 -0400 Received: from terminus.zytor.com ([198.137.202.10]:36447 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750968Ab0JVApw (ORCPT ); Thu, 21 Oct 2010 20:45:52 -0400 Message-ID: <4CC0DEB8.1060309@zytor.com> Date: Thu, 21 Oct 2010 17:45:44 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.9) Gecko/20100921 Fedora/3.1.4-1.fc13 Thunderbird/3.1.4 MIME-Version: 1.0 To: Jeremy Fitzhardinge CC: the arch/x86 maintainers , "Xen-devel@lists.xensource.com" , Linux Kernel Mailing List , Konrad Rzeszutek Wilk Subject: Re: [PATCH] x86: define arch_vm_get_page_prot to set _PAGE_IOMAP on VM_IO vmas References: <4CC0C14E.5080205@goop.org> <4CC0C318.90401@zytor.com> <4CC0CA07.3000306@goop.org> In-Reply-To: <4CC0CA07.3000306@goop.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/21/2010 04:17 PM, Jeremy Fitzhardinge wrote: > > Xen PV guests are always responsible for constructing ptes with machine > addresses in them (ie, doing their own pseudo-physical to machine > address conversion), and Xen verifies that the pages they want to map > either belong to them or have been granted to them. The _PAGE_IOMAP > flag is a kernel-internal one which allows us to distinguish between > ptes intended to map memory vs machine hardware addresses; it is not > part of the Xen ABI. > > If you're passing a device through to a domain, the domain is given > access to the device's address space so it can legally map those pages > (and if an IOMMU is available, the device is constrained to only DMA > that domain's memory). > Okay, could you clarify this part a bit? Why does the kernel need to know the difference between "pseudo-physical" and "machine addresses" at all? If they overlap, there is a problem, and if they don't overlap, it will be a 1:1 mapping anyway... -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.