From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:33436) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SAFAw-0001nh-Fa for qemu-devel@nongnu.org; Wed, 21 Mar 2012 02:37:39 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SAFAu-0004bv-5O for qemu-devel@nongnu.org; Wed, 21 Mar 2012 02:37:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42270) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SAFAt-0004bp-TS for qemu-devel@nongnu.org; Wed, 21 Mar 2012 02:37:36 -0400 Date: Wed, 21 Mar 2012 08:37:46 +0200 From: "Michael S. Tsirkin" Message-ID: <20120321063746.GA6773@redhat.com> References: <20120320062020.12815.61342.stgit@jason-ThinkPad-T400> <87ty1jpm6p.fsf@rustcorp.com.au> <20120320224805.GA4997@redhat.com> <87ty1ializ.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87ty1ializ.fsf@rustcorp.com.au> Subject: Re: [Qemu-devel] [PATCH] virtio-spec: clarify ro/rw bits and updating rule of virtio-net status field List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Rusty Russell Cc: qemu-devel@nongnu.org, Christian Borntraeger , Jason Wang , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org On Wed, Mar 21, 2012 at 10:10:52AM +1030, Rusty Russell wrote: > On Wed, 21 Mar 2012 00:48:05 +0200, "Michael S. Tsirkin" wrote: > > On Tue, Mar 20, 2012 at 09:35:18PM +1030, Rusty Russell wrote: > > > On Tue, 20 Mar 2012 14:20:21 +0800, Jason Wang wrote: > > > > This patch clarifies VIRTIO_NET_S_LINK_UP as a read-only bit and > > > > VIRTIO_NET_S_ANNOUNCE as a read-writable bit. Also introduce the write 1 to > > > > clear semantics for all read-writable bits of config status field. This could > > > > help to reduce the config status field updating race between host and guest and > > > > also simplify the implementation. > > > > > > > > Signed-off-by: Jason Wang > > > > > > This approach assumes an active config field, which neither lguest nor > > > S/390 have. > > > > > > Thanks, > > > Rusty. > > > > What does 'active' mean in this context? > > It means you are assuming that writes to the config field trap to the > host. > > Rusty. Ah. Right, we need to trap for host to clear the bit. OK, so let's make the bit RO, and add VIRTIO_NET_CTRL_ANNOUNCED to acknowledge that we've seen VIRTIO_NET_S_ANNOUNCE using the control VQ? If there's no ctrl VQ, we won't acknowledge the feature bit ... > -- > How could I marry someone with more hair than me? http://baldalex.org