netdev - Re: [RFC PATCH 3/5] uapi/linux/virtio

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Date:   Tue, 22 Feb 2022 15:14:44 +0200
From:   Andrew Melnichenko <andrew@...nix.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Network Development <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        virtualization <virtualization@...ts.linux-foundation.org>,
        Yuri Benditovich <yuri.benditovich@...nix.com>,
        Yan Vugenfirer <yan@...nix.com>
Subject: Re: [RFC PATCH 3/5] uapi/linux/virtio_net.h: Added USO types.

Hi all,



On Wed, Feb 9, 2022 at 6:41 AM Jason Wang <jasowang@...hat.com> wrote:
>
>
> 在 2022/1/25 下午4:47, Andrew Melnychenko 写道:
> > Added new GSO type for USO: VIRTIO_NET_HDR_GSO_UDP_L4.
> > Feature VIRTIO_NET_F_HOST_USO allows to enable NETIF_F_GSO_UDP_L4.
> > Separated VIRTIO_NET_F_GUEST_USO4 & VIRTIO_NET_F_GUEST_USO6 features
> > required for Windows guests.
> >
> > Signed-off-by: Andrew Melnychenko <andrew@...nix.com>
> > ---
> >   include/uapi/linux/virtio_net.h | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
> > index 3f55a4215f11..620addc5767b 100644
> > --- a/include/uapi/linux/virtio_net.h
> > +++ b/include/uapi/linux/virtio_net.h
> > @@ -56,6 +56,9 @@
> >   #define VIRTIO_NET_F_MQ     22      /* Device supports Receive Flow
> >                                        * Steering */
> >   #define VIRTIO_NET_F_CTRL_MAC_ADDR 23       /* Set MAC address */
> > +#define VIRTIO_NET_F_GUEST_USO4      54      /* Guest can handle USOv4 in. */
> > +#define VIRTIO_NET_F_GUEST_USO6      55      /* Guest can handle USOv6 in. */
> > +#define VIRTIO_NET_F_HOST_USO        56      /* Host can handle USO in. */
>
>
> I think it's better to be consistent here. Either we split in both guest
> and host or not.
>
> Thanks
>

The main reason that receives USO packets depends on the kernel, where
transmitting the feature that VirtIO implements.
Windows systems have the option to manipulate receive offload. That's
why there are two GUEST_USO features.
For HOST_USO - technically there is no point in "split" it, and there
is should not be any difference between IPv4/IPv6.
Technically, we either support transmitting big UDP packets or not.

>
> >
> >   #define VIRTIO_NET_F_HASH_REPORT  57        /* Supports hash report */
> >   #define VIRTIO_NET_F_RSS      60    /* Supports RSS RX steering */
> > @@ -130,6 +133,7 @@ struct virtio_net_hdr_v1 {
> >   #define VIRTIO_NET_HDR_GSO_TCPV4    1       /* GSO frame, IPv4 TCP (TSO) */
> >   #define VIRTIO_NET_HDR_GSO_UDP              3       /* GSO frame, IPv4 UDP (UFO) */
> >   #define VIRTIO_NET_HDR_GSO_TCPV6    4       /* GSO frame, IPv6 TCP */
> > +#define VIRTIO_NET_HDR_GSO_UDP_L4    5       /* GSO frame, IPv4 & IPv6 UDP (USO) */
> >   #define VIRTIO_NET_HDR_GSO_ECN              0x80    /* TCP has ECN set */
> >       __u8 gso_type;
> >       __virtio16 hdr_len;     /* Ethernet + IP + tcp/udp hdrs */
>