From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1LBunE-0007V8-6q for qemu-devel@nongnu.org; Sun, 14 Dec 2008 12:30:12 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LBunD-0007Tv-FG for qemu-devel@nongnu.org; Sun, 14 Dec 2008 12:30:11 -0500 Received: from [199.232.76.173] (port=41931 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LBunC-0007Ti-KQ for qemu-devel@nongnu.org; Sun, 14 Dec 2008 12:30:10 -0500 Received: from mail2.shareable.org ([80.68.89.115]:37975) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1LBunC-0006cH-8Z for qemu-devel@nongnu.org; Sun, 14 Dec 2008 12:30:10 -0500 Date: Sun, 14 Dec 2008 17:30:05 +0000 From: Jamie Lokier Subject: Re: [Qemu-devel] Re: [PATCH 2 of 5] add can_dma/post_dma for direct IO 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 Content-Disposition: inline In-Reply-To: <4942BDEE.7020003@codemonkey.ws> Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Andrea Arcangeli , chrisw@redhat.com, avi@redhat.com, kvm@vger.kernel.org, Gerd Hoffmann 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