On Thu, Dec 21, 2017 at 01:37:29PM +0200, Yan Vugenfirer wrote:
> 
> > On 20 Dec 2017, at 17:00, Michael S. Tsirkin <[email protected]> wrote:
> > 
> > On Thu, Dec 14, 2017 at 03:31:54PM -0500, Jason Baron wrote:
> >> Hi,
> >> 
> >> We have found it useful to have the virtio net device export a linkspeed
> >> and duplex setting, such that a guest linkspeed and duplex settings can
> >> be set automatically from the host side. We have some guest software
> >> that relies on this setting, and fails without a valid value provided.
> > 
> > That software really should be fixed btw. You can't always reliably
> > figure out the speed, and it might change at any time.
> > 
> Good point. Each time when there is a linked up indication from the host, we 
> should expect that the settings can be different (for example backend 
> changed).

Interesting.

So far the motivation was just to trick some proprietary software,
for that a static field might be enough.

If not - what is the motivation exactly? 


> >> Thus, I would like to propose adding a new feature bit:
> >> 
> >> VIRTIO_NET_F_SPEED_DUPLEX (4) Device provides a linkspeed and duplex 
> >> setting
> > 
> > 
> > I think a high feature bit would be better. Low bits can be
> > backported to legacy devices, so better used for things
> > like mtu, where communication just breaks otherwise,
> > and for net we are running out of these.
> > 
> > 
> >> I have provided sample qemu hypervisor and linux kernel guest code to
> >> implement this feature here:
> >> 
> >> http://lkml.iu.edu/hypermail/linux/kernel/1712.1/05692.html
> >> 
> >> Thanks,
> >> 
> >> -Jason
> > 
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