netdev - Re: [PATCH net] virtio-net: restore VIRTIO_HDR_F_DATA

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Message-ID: <268cadeb-433c-7960-5fe6-a06f849493a8@redhat.com>
Date:   Sun, 22 Jan 2017 10:41:22 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        Rolf Neugebauer <rolf.neugebauer@...ker.com>
Subject: Re: [PATCH net] virtio-net: restore VIRTIO_HDR_F_DATA_VALID on
 receiving



On 2017年01月21日 00:45, Michael S. Tsirkin wrote:
> On Fri, Jan 20, 2017 at 02:32:42PM +0800, Jason Wang wrote:
>> Commit 501db511397f ("virtio: don't set VIRTIO_NET_HDR_F_DATA_VALID on
>> xmit") in fact disables VIRTIO_HDR_F_DATA_VALID on receiving path too,
>> fixing this by adding a hint (has_data_valid) and set it only on the
>> receiving path.
>>
>> Cc: Rolf Neugebauer<rolf.neugebauer@...ker.com>
>> Signed-off-by: Jason Wang<jasowang@...hat.com>
>> ---
>>   drivers/net/macvtap.c      | 2 +-
>>   drivers/net/tun.c          | 2 +-
>>   drivers/net/virtio_net.c   | 2 +-
>>   include/linux/virtio_net.h | 6 +++++-
>>   net/packet/af_packet.c     | 4 ++--
>>   5 files changed, 10 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
>> index 5c26653..4026185 100644
>> --- a/drivers/net/macvtap.c
>> +++ b/drivers/net/macvtap.c
>> @@ -825,7 +825,7 @@ static ssize_t macvtap_put_user(struct macvtap_queue *q,
>>   			return -EINVAL;
>>   
>>   		if (virtio_net_hdr_from_skb(skb, &vnet_hdr,
>> -					    macvtap_is_little_endian(q)))
>> +					    macvtap_is_little_endian(q), true))
>>   			BUG();
>>   
>>   		if (copy_to_iter(&vnet_hdr, sizeof(vnet_hdr), iter) !=
>> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
>> index cd8e02c..2cd10b2 100644
>> --- a/drivers/net/tun.c
>> +++ b/drivers/net/tun.c
>> @@ -1360,7 +1360,7 @@ static ssize_t tun_put_user(struct tun_struct *tun,
>>   			return -EINVAL;
>>   
>>   		if (virtio_net_hdr_from_skb(skb, &gso,
>> -					    tun_is_little_endian(tun))) {
>> +					    tun_is_little_endian(tun), true)) {
>>   			struct skb_shared_info *sinfo = skb_shinfo(skb);
>>   			pr_err("unexpected GSO type: "
>>   			       "0x%x, gso_size %d, hdr_len %d\n",
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 4a10500..3474243 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -1104,7 +1104,7 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
>>   		hdr = skb_vnet_hdr(skb);
>>   
>>   	if (virtio_net_hdr_from_skb(skb, &hdr->hdr,
>> -				    virtio_is_little_endian(vi->vdev)))
>> +				    virtio_is_little_endian(vi->vdev), false))
>>   		BUG();
>>   
>>   	if (vi->mergeable_rx_bufs)
>> diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
>> index 5643647..5209b5e 100644
>> --- a/include/linux/virtio_net.h
>> +++ b/include/linux/virtio_net.h
>> @@ -56,7 +56,8 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
>>   
>>   static inline int virtio_net_hdr_from_skb(const struct sk_buff *skb,
>>   					  struct virtio_net_hdr *hdr,
>> -					  bool little_endian)
>> +					  bool little_endian,
>> +					  bool has_data_valid)
>>   {
>>   	memset(hdr, 0, sizeof(*hdr));   /* no info leak */
>>   
> I would prefer naming it is_rx. Callers should not know about
> internal details like data valid, the issue we are trying to fix
> here is that tx and tx headers are slightly different.
>

Actually, I've considered something like this, but the problem is:

- tun use this on xmit, so is_rx = true may cause some confusion here
- I believe we may want to support DATA_VALID (like xen-netback) on tx 
(probably with a feature) in the future.

Thanks