netdev - Re: [PATCH 1/4] virtio-net: add definitions for host USO feature

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Date:   Wed, 12 May 2021 09:21:31 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Yuri Benditovich <yuri.benditovich@...nix.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>,
        Yan Vugenfirer <yan@...nix.com>
Subject: Re: [PATCH 1/4] virtio-net: add definitions for host USO feature


在 2021/5/11 下午5:21, Yuri Benditovich 写道:
> On Tue, May 11, 2021 at 11:24 AM Jason Wang <jasowang@...hat.com> wrote:
>> On Tue, May 11, 2021 at 4:12 PM Yuri Benditovich
>> <yuri.benditovich@...nix.com> wrote:
>>> On Tue, May 11, 2021 at 9:47 AM Jason Wang <jasowang@...hat.com> wrote:
>>>>
>>>> 在 2021/5/11 下午12:42, Yuri Benditovich 写道:
>>>>> Define feature bit and GSO type according to the VIRTIO
>>>>> specification.
>>>>>
>>>>> Signed-off-by: Yuri Benditovich <yuri.benditovich@...nix.com>
>>>>> ---
>>>>>    include/uapi/linux/virtio_net.h | 2 ++
>>>>>    1 file changed, 2 insertions(+)
>>>>>
>>>>> diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
>>>>> index 3f55a4215f11..a556ac735d7f 100644
>>>>> --- a/include/uapi/linux/virtio_net.h
>>>>> +++ b/include/uapi/linux/virtio_net.h
>>>>> @@ -57,6 +57,7 @@
>>>>>                                         * Steering */
>>>>>    #define VIRTIO_NET_F_CTRL_MAC_ADDR 23       /* Set MAC address */
>>>>>
>>>>> +#define VIRTIO_NET_F_HOST_USO     56 /* Host can handle USO packets */
>>> This is the virtio-net feature
>> Right, I miss this part.
>>
>>>>>    #define VIRTIO_NET_F_HASH_REPORT  57        /* Supports hash report */
>>>>>    #define VIRTIO_NET_F_RSS      60    /* Supports RSS RX steering */
>>>>>    #define VIRTIO_NET_F_RSC_EXT          61    /* extended coalescing info */
>>>>> @@ -130,6 +131,7 @@ 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 UDP (USO) */
>>> This is respective GSO type
>>>
>>>>
>>>> This is the gso_type not the feature actually.
>>>>
>>>> I wonder what's the reason for not
>>>>
>>>> 1) introducing a dedicated virtio-net feature bit for this
>>>> (VIRTIO_NET_F_GUEST_GSO_UDP_L4.
>>> This series is not for GUEST's feature, it is only for host feature.
>>>
>>>> 2) toggle the NETIF_F_GSO_UDP_L4  feature for tuntap based on the
>>>> negotiated feature.
>>> The NETIF_F_GSO_UDP_L4 would be required for the guest RX path.
>>> The guest TX path does not require any flags to be propagated, it only
>>> allows the guest to transmit large UDP packets and have them
>>> automatically splitted.
>>> (This is similar to HOST_UFO but does packet segmentation instead of
>>> fragmentation. GUEST_UFO indeed requires a respective NETIF flag, as
>>> it is unclear whether the guest is capable of receiving such packets).
>> So I think it's better to implement TX/RX in the same series unless
>> there's something missed:
>>
>> For Guest TX, NETIF_F_GSO_UDP_L4 needs to be enabled in the guest
>> virtio-net only when VIRTIO_NET_F_HOST_USO is negotiated.
> I understand that this is what should be done when this feature will
> be added to Linux virtio-net driver.
> But at the moment we do not have enough resources to work on it.
> Currently we have a clear use case and ability to test in on Windows guest.
> Respective QEMU changes are pending for kernel patches, current
> reference is https://github.com/daynix/qemu/tree/uso


This looks fine but as replied in another thread.

We can test both TX and RX with Linux guests simply:

We can just use 2 VMs, and let one VM send GSO_UDP_L4 packet to another, 
then both tx and rx in both guest (virtio-net) and host (virtio-net) are 
tested?

Thanks


>
>> For guest RX, NETIF_F_GSO_UDP_L4 needs to be enabled on the host
>> tuntap only when VIRTIO_NET_F_GUEST_USO is neogiated.
> Currently we are not able to use guest RX UDP GSO.
> In order to do that we at least should be able to build our Windows
> drivers with the most updated driver development kit (2004+).
> At the moment we can't, this task is in a plan but can take several
> months. So we do not have a test/use case with Windows VM.
>
>
>> Thanks
>>
>>>> Thanks
>>>>
>>>>
>>>>>    #define VIRTIO_NET_HDR_GSO_ECN              0x80    /* TCP has ECN set */
>>>>>        __u8 gso_type;
>>>>>        __virtio16 hdr_len;     /* Ethernet + IP + tcp/udp hdrs */