From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45469) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eWjQ7-0005lb-VY for qemu-devel@nongnu.org; Wed, 03 Jan 2018 08:49:28 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eWjQ4-0005cH-Qy for qemu-devel@nongnu.org; Wed, 03 Jan 2018 08:49:28 -0500 Received: from mx1.redhat.com ([209.132.183.28]:45004) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eWjQ4-0005bt-KV for qemu-devel@nongnu.org; Wed, 03 Jan 2018 08:49:24 -0500 Date: Wed, 3 Jan 2018 15:49:21 +0200 From: "Michael S. Tsirkin" Message-ID: <20180103154824-mutt-send-email-mst@kernel.org> References: <1513979641-7999-1-git-send-email-jbaron@akamai.com> <44da522ecee60792ec918234ee4d61a84e4574f0.1513974243.git.jbaron@akamai.com> <20171227.164334.2079471466039224265.davem@davemloft.net> <93b66082-f37c-0463-e977-d4b430a44008@akamai.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <93b66082-f37c-0463-e977-d4b430a44008@akamai.com> Subject: Re: [Qemu-devel] [PATCH net-next v2 1/3] virtio_net: propagate linkspeed/duplex settings from the hypervisor List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jason Baron Cc: David Miller , netdev@vger.kernel.org, virtualization@lists.linux-foundation.org, qemu-devel@nongnu.org, jasowang@redhat.com On Thu, Dec 28, 2017 at 10:53:54AM -0500, Jason Baron wrote: > > > On 12/27/2017 04:43 PM, David Miller wrote: > > From: Jason Baron > > Date: Fri, 22 Dec 2017 16:54:01 -0500 > > > >> The ability to set speed and duplex for virtio_net in useful in various > >> scenarios as described here: > >> > >> 16032be virtio_net: add ethtool support for set and get of settings > >> > >> However, it would be nice to be able to set this from the hypervisor, > >> such that virtio_net doesn't require custom guest ethtool commands. > >> > >> Introduce a new feature flag, VIRTIO_NET_F_SPEED_DUPLEX, which allows > >> the hypervisor to export a linkspeed and duplex setting. The user can > >> subsequently overwrite it later if desired via: 'ethtool -s'. > >> > >> Signed-off-by: Jason Baron > >> Cc: "Michael S. Tsirkin" > >> Cc: Jason Wang > > > > Looks mostly fine to me but need some virtio_net reviewers on this one. > > > >> @@ -57,6 +57,8 @@ > >> * Steering */ > >> #define VIRTIO_NET_F_CTRL_MAC_ADDR 23 /* Set MAC address */ > >> > >> +#define VIRTIO_NET_F_SPEED_DUPLEX 63 /* Host set linkspeed and duplex */ > >> + > > > > Why use a value so far away from the largest existing one? > > > > Just curious. > > > > So that came from a discussion with Michael about which bit to use for > this, and he suggested using 63: > > " > Transports started from bit 24 and are growing up. > So I would say devices should start from bit 63 and grow down. > " > > https://patchwork.ozlabs.org/patch/848814/#1826669 > > I will add a comment to explain it. Maybe in the commit log. I don't think we need it in the header. > Thanks, > > -Jason