From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jamie Lokier Subject: Re: [Qemu-devel] Re: [PATCH 2 of 5] add can_dma/post_dma for direct IO Date: Sun, 14 Dec 2008 17:30:05 +0000 Message-ID: <20081214173001.GC28984@shareable.org> References: <4942B841.6010900@codemonkey.ws> <4942BDEE.7020003@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andrea Arcangeli , chrisw@redhat.com, avi@redhat.com, Gerd Hoffmann , kvm@vger.kernel.org To: qemu-devel@nongnu.org Return-path: Received: from mail2.shareable.org ([80.68.89.115]:41193 "EHLO mail2.shareable.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753545AbYLNRaL (ORCPT ); Sun, 14 Dec 2008 12:30:11 -0500 Content-Disposition: inline In-Reply-To: <4942BDEE.7020003@codemonkey.ws> Sender: kvm-owner@vger.kernel.org List-ID: Anthony Liguori wrote: > Let me clarify this a bit more. The problem we're trying to address > today is the encapsulating knowledge of phys_ram_base. We want to > minimize the amount of code that makes any assumptions about > phys_ram_base. Your current API still accesses phys_ram_base directly > in the PCI DMA API. The only real improvement compared to the current > virtio code is that you properly handle MMIO. This is not just about > layout but this also includes the fact that in the future, guest memory > could be discontiguous in QEMU (think memory hotplug). One little extra thing: What about PCI DMA to another PCI device, not to RAM? That's not used very often, but it ought to work. -- Jamie