On 12/27/2017 04:43 PM, David Miller wrote: > From: Jason Baron <jba...@akamai.com> > 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 <jba...@akamai.com> >> Cc: "Michael S. Tsirkin" <m...@redhat.com> >> Cc: Jason Wang <jasow...@redhat.com> > > 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. Thanks, -Jason
