From mboxrd@z Thu Jan 1 00:00:00 1970 From: Muli Ben-Yehuda Subject: Re: [PATCH v2 -mm 0/2] x86: per-device dma_mapping_ops Date: Sun, 25 May 2008 10:20:11 +0300 Message-ID: <20080525072011.GM7334@il.ibm.com> References: <1211178689-3507-1-git-send-email-fujita.tomonori@lab.ntt.co.jp> <200805221613.03686.amit.shah@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: FUJITA Tomonori , linux-kernel@vger.kernel.org, akpm@linux-foundation.org, alexisb@us.ibm.com, andi@firstfloor.org, kvm@vger.kernel.org, avi@qumranet.com To: Amit Shah Return-path: Received: from mtagate2.de.ibm.com ([195.212.29.151]:26872 "EHLO mtagate2.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751835AbYEYHUP (ORCPT ); Sun, 25 May 2008 03:20:15 -0400 Content-Disposition: inline In-Reply-To: <200805221613.03686.amit.shah@qumranet.com> Sender: kvm-owner@vger.kernel.org List-ID: On Thu, May 22, 2008 at 04:13:02PM +0530, Amit Shah wrote: > OK; this sounds helpful. the hook can make a hypercall and confirm > with the host kernel if the device in question is an assigned > physical device. If yes, we replace the dma_ops. Though, the > original intent of having stackable ops is that we might want to go > through the swiotlb in the guest even for an assigned device if the > guest dma addresses are not in the addressable range of the guest > chipset. > > > created (it works with hot plugging). It enables IOMMUs to set up an > > appropriate dma_mapping_ops per device. > > From what we've discussed so far, it looks like stackable dma ops will > definitely be needed. Does this patchset provide something that stacking > won't? Yes---this patchset let's you have a per-device dma-ops, whereas with stackable you only get global dma-ops. I think it's clear we need both, and I think per-device dma-ops are the first thing that's needed. Stacking can then be introduced on a per-device basis. Cheers, Muli