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Tsirkin" Cc: Jonathan Corbet , Willem de Bruijn , Jason Wang , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Xuan Zhuo , Shuah Khan , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kselftest@vger.kernel.org, Yuri Benditovich , Andrew Melnychenko , Stephen Hemminger , gur.stavi@huawei.com, devel@daynix.com References: <20250109-tun-v2-0-388d7d5a287a@daynix.com> <20250109-tun-v2-3-388d7d5a287a@daynix.com> <20250109023144-mutt-send-email-mst@kernel.org> <20250109023829-mutt-send-email-mst@kernel.org> <20250109055425-mutt-send-email-mst@kernel.org> Content-Language: en-US From: Akihiko Odaki In-Reply-To: <20250109055425-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2025/01/09 19:54, Michael S. Tsirkin wrote: > On Thu, Jan 09, 2025 at 06:38:10PM +0900, Akihiko Odaki wrote: >> On 2025/01/09 16:40, Michael S. Tsirkin wrote: >>> On Thu, Jan 09, 2025 at 02:32:25AM -0500, Michael S. Tsirkin wrote: >>>> On Thu, Jan 09, 2025 at 03:58:45PM +0900, Akihiko Odaki wrote: >>>>> The specification says the device MUST set num_buffers to 1 if >>>>> VIRTIO_NET_F_MRG_RXBUF has not been negotiated. >>>>> >>>>> Signed-off-by: Akihiko Odaki >>>> >>>> >>>> How do we know this is v1 and not v0? Confused. >>> >>> Ah I got it, you assume userspace will over-write it >>> if VIRTIO_NET_F_MRG_RXBUF is set. >>> If we are leaving this up to userspace, why not let it do >>> it always? >> >> tun may be used with vhost_net, which does not set the field. > > I'd fix that in vhost net. Let's see what filesystem and networking people will say for the earlier patch. We can fix num_buffers for free if the earlier patch is getting merged. We will need to come up with another solution otherwise. > > >>> >>>>> --- >>>>> drivers/net/tap.c | 2 +- >>>>> drivers/net/tun.c | 6 ++++-- >>>>> drivers/net/tun_vnet.c | 14 +++++++++----- >>>>> drivers/net/tun_vnet.h | 4 ++-- >>>>> 4 files changed, 16 insertions(+), 10 deletions(-) >>>>> >>>>> diff --git a/drivers/net/tap.c b/drivers/net/tap.c >>>>> index 60804855510b..fe9554ee5b8b 100644 >>>>> --- a/drivers/net/tap.c >>>>> +++ b/drivers/net/tap.c >>>>> @@ -713,7 +713,7 @@ static ssize_t tap_put_user(struct tap_queue *q, >>>>> int total; >>>>> if (q->flags & IFF_VNET_HDR) { >>>>> - struct virtio_net_hdr vnet_hdr; >>>>> + struct virtio_net_hdr_v1 vnet_hdr; >>>>> vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz); >>>>> diff --git a/drivers/net/tun.c b/drivers/net/tun.c >>>>> index dbf0dee92e93..f211d0580887 100644 >>>>> --- a/drivers/net/tun.c >>>>> +++ b/drivers/net/tun.c >>>>> @@ -1991,7 +1991,9 @@ static ssize_t tun_put_user_xdp(struct tun_struct *tun, >>>>> size_t total; >>>>> if (tun->flags & IFF_VNET_HDR) { >>>>> - struct virtio_net_hdr gso = { 0 }; >>>>> + struct virtio_net_hdr_v1 gso = { >>>>> + .num_buffers = __virtio16_to_cpu(true, 1) >>>>> + }; >>>>> vnet_hdr_sz = READ_ONCE(tun->vnet_hdr_sz); >>>>> ret = tun_vnet_hdr_put(vnet_hdr_sz, iter, &gso); >>>>> @@ -2044,7 +2046,7 @@ static ssize_t tun_put_user(struct tun_struct *tun, >>>>> } >>>>> if (vnet_hdr_sz) { >>>>> - struct virtio_net_hdr gso; >>>>> + struct virtio_net_hdr_v1 gso; >>>>> ret = tun_vnet_hdr_from_skb(tun->flags, tun->dev, skb, &gso); >>>>> if (ret < 0) >>>>> diff --git a/drivers/net/tun_vnet.c b/drivers/net/tun_vnet.c >>>>> index ffb2186facd3..a7a7989fae56 100644 >>>>> --- a/drivers/net/tun_vnet.c >>>>> +++ b/drivers/net/tun_vnet.c >>>>> @@ -130,15 +130,17 @@ int tun_vnet_hdr_get(int sz, unsigned int flags, struct iov_iter *from, >>>>> EXPORT_SYMBOL_GPL(tun_vnet_hdr_get); >>>>> int tun_vnet_hdr_put(int sz, struct iov_iter *iter, >>>>> - const struct virtio_net_hdr *hdr) >>>>> + const struct virtio_net_hdr_v1 *hdr) >>>>> { >>>>> + int content_sz = MIN(sizeof(*hdr), sz); >>>>> + >>>>> if (iov_iter_count(iter) < sz) >>>>> return -EINVAL; >>>>> - if (copy_to_iter(hdr, sizeof(*hdr), iter) != sizeof(*hdr)) >>>>> + if (copy_to_iter(hdr, content_sz, iter) != content_sz) >>>>> return -EFAULT; >>>>> - if (iov_iter_zero(sz - sizeof(*hdr), iter) != sz - sizeof(*hdr)) >>>>> + if (iov_iter_zero(sz - content_sz, iter) != sz - content_sz) >>>>> return -EFAULT; >>>>> return 0; >>>>> @@ -154,11 +156,11 @@ EXPORT_SYMBOL_GPL(tun_vnet_hdr_to_skb); >>>>> int tun_vnet_hdr_from_skb(unsigned int flags, const struct net_device *dev, >>>>> const struct sk_buff *skb, >>>>> - struct virtio_net_hdr *hdr) >>>>> + struct virtio_net_hdr_v1 *hdr) >>>>> { >>>>> int vlan_hlen = skb_vlan_tag_present(skb) ? VLAN_HLEN : 0; >>>>> - if (virtio_net_hdr_from_skb(skb, hdr, >>>>> + if (virtio_net_hdr_from_skb(skb, (struct virtio_net_hdr *)hdr, >>>>> tun_vnet_is_little_endian(flags), true, >>>>> vlan_hlen)) { >>>>> struct skb_shared_info *sinfo = skb_shinfo(skb); >>>>> @@ -176,6 +178,8 @@ int tun_vnet_hdr_from_skb(unsigned int flags, const struct net_device *dev, >>>>> return -EINVAL; >>>>> } >>>>> + hdr->num_buffers = 1; >>>>> + >>>>> return 0; >>>>> } >>>>> EXPORT_SYMBOL_GPL(tun_vnet_hdr_from_skb); >>>>> diff --git a/drivers/net/tun_vnet.h b/drivers/net/tun_vnet.h >>>>> index 2dfdbe92bb24..d8fd94094227 100644 >>>>> --- a/drivers/net/tun_vnet.h >>>>> +++ b/drivers/net/tun_vnet.h >>>>> @@ -12,13 +12,13 @@ int tun_vnet_hdr_get(int sz, unsigned int flags, struct iov_iter *from, >>>>> struct virtio_net_hdr *hdr); >>>>> int tun_vnet_hdr_put(int sz, struct iov_iter *iter, >>>>> - const struct virtio_net_hdr *hdr); >>>>> + const struct virtio_net_hdr_v1 *hdr); >>>>> int tun_vnet_hdr_to_skb(unsigned int flags, struct sk_buff *skb, >>>>> const struct virtio_net_hdr *hdr); >>>>> int tun_vnet_hdr_from_skb(unsigned int flags, const struct net_device *dev, >>>>> const struct sk_buff *skb, >>>>> - struct virtio_net_hdr *hdr); >>>>> + struct virtio_net_hdr_v1 *hdr); >>>>> #endif /* TUN_VNET_H */ >>>>> >>>>> -- >>>>> 2.47.1 >>> >