Re: [Qemu-devel] [PATCH 1/2 V3] virtio-spec: dynamic network offloads configuration

[Rusty Russell]

Dmitry Fleytman <address@hidden> writes:
> From: Dmitry Fleytman <address@hidden>
>
> Virtio-net driver currently negotiates network offloads
> on startup via features mechanism and have no ability to
> change offloads state later.
> This patch introduced a new control command that allows
> to configure device network offloads state dynamically.
> The patch also introduces a new feature flag
> VIRTIO_NET_F_CTRL_GUEST_OFFLOADS.
>
> Signed-off-by: Dmitry Fleytman <address@hidden>

(BTW, I like to be CC'd on these things directly, so I don't miss them)

The idea is fine.

But I dislike the duplication of constants: let's just use the feature
bits directly:

#define VIRTIO_NET_F_GUEST_CSUM 1       /* Guest handles pkts w/ partial csum */
#define VIRTIO_NET_F_GUEST_TSO4 7       /* Guest can handle TSOv4 in. */
#define VIRTIO_NET_F_GUEST_TSO6 8       /* Guest can handle TSOv6 in. */
#define VIRTIO_NET_F_GUEST_ECN  9       /* Guest can handle TSO[6] w/ ECN in. */
#define VIRTIO_NET_F_GUEST_UFO  10      /* Guest can handle UFO in. */

You want this, because you have to test against them anyway before
trying to re-enable them.

And secondly, it'll be much clearer if you don't say "change" but
"disable and re-enable", which is what's actually allowed.

Thanks,
Rusty.