From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH 9/9] x86/iommu: use dma_ops_list in get_dma_ops Date: Mon, 29 Sep 2008 11:29:17 +0200 Message-ID: <20080929092917.GO27426@8bytes.org> References: <1222107681-8185-1-git-send-email-joerg.roedel@amd.com> <1222107681-8185-10-git-send-email-joerg.roedel@amd.com> <20080928231211X.fujita.tomonori@lab.ntt.co.jp> <20080928184424.GA26563@8bytes.org> <20080929092549.GA6931@il.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: FUJITA Tomonori , joerg.roedel@amd.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, iommu@lists.linux-foundation.org, dwmw2@infradead.org, amit.shah@qumranet.com, mingo@redhat.com To: Muli Ben-Yehuda Return-path: Received: from 8bytes.org ([88.198.83.132]:51430 "EHLO 8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754651AbYI2J3T (ORCPT ); Mon, 29 Sep 2008 05:29:19 -0400 Content-Disposition: inline In-Reply-To: <20080929092549.GA6931@il.ibm.com> Sender: kvm-owner@vger.kernel.org List-ID: On Mon, Sep 29, 2008 at 12:25:49PM +0300, Muli Ben-Yehuda wrote: > On Sun, Sep 28, 2008 at 08:44:24PM +0200, Joerg Roedel wrote: > > > Hmm, we should only call find_dma_ops_for_device() the first time a > > dma api call is done (look into get_dma_ops). But I also thought > > about how this lock can be avoided. In the real world it should not > > be necessary because the dma_ops list is initialized before dma api > > calls are done. But since there is now a register function which can > > be called its safer this way. What do you think, are we still safe > > enough without this lock? > > We could be, if we add a check to the register function that verifies > it isn't being called after DMAs have started. Something like: > > in register: > > if (dma_started) > yell loudly > > before PCI device initialization and after IOMMU initialization: > dma_started = true Good idea. I will change this in my patchset, thanks. Joerg