From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: virtio & hypercall interface? Date: Sat, 15 Sep 2007 11:05:25 +0300 Message-ID: <46EB9245.4010005@qumranet.com> References: <1189664514.32322.14.camel@localhost.localdomain> <64F9B87B6B770947A9F8391472E032160DA17EF2@ehost011-8.exch011.intermedia.net> <46E9A17D.5040205@us.ibm.com> <46EABAD0.40300@qumranet.com> <46EB0BD8.6040000@qumranet.com> <1189825560.7262.77.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel To: Rusty Russell Return-path: In-Reply-To: <1189825560.7262.77.camel-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Rusty Russell wrote: > On Sat, 2007-09-15 at 01:31 +0300, Dor Laor wrote: > >> Second, regardless of the channel signal notification, there are still >> real necessities for userspace hypercall handling: >> 1. For virtio drivers there is also registration hypercall for passing >> the shared memory pfns. >> Sure there are other possibilities, but why limit ourselves? >> > > I really prefer doing this the more "hardware-like" way and having the > device description say where the pages are. Surely this is simpler from > the qemu side, too? > This is mmio style (device provides memory). DMA style (guest provides memory, device dmas it) is easier for kvm: we don't need to allocate a new memory slot, and migration is easier. Most current hardware place the descriptor ring in guest memory, not the device, since mmio is slower for the cpu than RAM. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/