> -----Original Message----- > From: Michael S. Tsirkin <[email protected]> > Sent: Monday, February 2, 2026 6:20 PM > To: Chia-Yu Chang (Nokia) <[email protected]> > Cc: [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; Koen De Schepper (Nokia) > <[email protected]>; [email protected]; > [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected] > Subject: Re: [PATCH v1 net-next 3/3] virtio_net: Accurate ECN flag in > virtio_net_hdr > > > CAUTION: This is an external email. Please be very careful when clicking > links or opening attachments. See the URL nok.it/ext for additional > information. > > > > On Mon, Feb 02, 2026 at 04:56:38PM +0000, Chia-Yu Chang (Nokia) wrote: > > > -----Original Message----- > > > From: Michael S. Tsirkin <[email protected]> > > > Sent: Sunday, February 1, 2026 10:18 AM > > > To: Chia-Yu Chang (Nokia) <[email protected]> > > > Cc: [email protected]; [email protected]; > > > [email protected]; [email protected]; [email protected]; > > > [email protected]; [email protected]; [email protected]; > > > [email protected]; [email protected]; [email protected]; > > > [email protected]; [email protected]; > > > [email protected]; [email protected]; [email protected]; > > > [email protected]; [email protected]; [email protected]; > > > [email protected]; [email protected]; [email protected]; > > > [email protected]; [email protected]; [email protected]; > > > [email protected]; [email protected]; > > > [email protected]; [email protected]; [email protected]; > > > [email protected]; [email protected]; [email protected]; > > > [email protected]; [email protected]; > > > [email protected]; [email protected]; > > > [email protected]; Koen De Schepper (Nokia) > > > <[email protected]>; [email protected]; > > > [email protected]; [email protected]; > > > [email protected]; [email protected]; [email protected]; > > > [email protected] > > > Subject: Re: [PATCH v1 net-next 3/3] virtio_net: Accurate ECN flag > > > in virtio_net_hdr > > > > > > > > > CAUTION: This is an external email. Please be very careful when clicking > > > links or opening attachments. See the URL nok.it/ext for additional > > > information. > > > > > > > > > > > > Thanks for the patch! Yet something to improve: > > > > > > On Sat, Jan 31, 2026 at 11:55:10PM +0100, > > > [email protected] wrote: > > > > From: Chia-Yu Chang <[email protected]> > > > > > > > > Unlike RFC 3168 ECN, accurate ECN uses the CWR flag as part of the > > > > ACE field to count new packets with CE mark; however, it will be > > > > corrupted by the RFC 3168 ECN-aware TSO. Therefore, fallback shall > > > > be applied by seting NETIF_F_GSO_ACCECN to ensure that the CWR > > > > flag should not be changed within a super-skb. > > > > > > > > To apply the aforementieond new AccECN GSO for virtio, new featue > > > > bits for host and guest are added for feature negotiation between > > > > driver and device. And the translation of Accurate ECN GSO flag > > > > between virtio_net_hdr and skb header for NETIF_F_GSO_ACCECN is > > > > also added to avoid CWR flag corruption due to RFC3168 ECN TSO. > > > > > > > > Signed-off-by: Chia-Yu Chang <[email protected]> > > > > > > > > > To the best of my understanding, this is a new feature - support for > > > VIRTIO_NET_F_HOST_ACCECN, VIRTIO_NET_F_GUEST_ACCECN? > > > The commit log makes it sound like it fixes some behaviour for existing > > > hardware, but that is not the case. > > > > > > > Thansk for the feedback, I will update commit message in v3. > > > > > > > --- > > > > v2: > > > > - Replace VIRTIO_NET_HDR_GSO_ECN with VIRTIO_NET_HDR_GSO_ECN_FLAGS > > > > > > but where is v2? this is v1... > > > > I shall update this version as v2, will do at the next version. > > > > [...] > > > > diff --git a/include/uapi/linux/virtio_net.h > > > > b/include/uapi/linux/virtio_net.h index 1db45b01532b..af5bfe45aa1f > > > > 100644 > > > > --- a/include/uapi/linux/virtio_net.h > > > > +++ b/include/uapi/linux/virtio_net.h > > > > @@ -56,6 +56,8 @@ > > > > #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_HOST_ACCECN 25 /* Host can handle GSO of > > > > +AccECN */ #define VIRTIO_NET_F_GUEST_ACCECN 26 /* Guest can > > > > +handle GSO of AccECN */ > > > > #define VIRTIO_NET_F_DEVICE_STATS 50 /* Device can provide > > > > device-level statistics. */ #define VIRTIO_NET_F_VQ_NOTF_COAL 52 /* > > > > Device supports virtqueue notification coalescing */ > > > > #define VIRTIO_NET_F_NOTF_COAL 53 /* Device supports > > > > notifications coalescing */ > > > > @@ -165,6 +167,9 @@ struct virtio_net_hdr_v1 { #define > > > > VIRTIO_NET_HDR_GSO_UDP_TUNNEL (VIRTIO_NET_HDR_GSO_UDP_TUNNEL_IPV4 | \ > > > > VIRTIO_NET_HDR_GSO_UDP_TUNNEL_IPV6) > > > > #define VIRTIO_NET_HDR_GSO_ECN 0x80 /* TCP has ECN > > > > set */ > > > > +#define VIRTIO_NET_HDR_GSO_ACCECN 0x10 /* TCP AccECN > > > > segmentation */ > > > > +#define VIRTIO_NET_HDR_GSO_ECN_FLAGS (VIRTIO_NET_HDR_GSO_ECN | \ > > > > + VIRTIO_NET_HDR_GSO_ACCECN) > > > > __u8 gso_type; > > > > __virtio16 hdr_len; /* Ethernet + IP + tcp/udp hdrs */ > > > > __virtio16 gso_size; /* Bytes to append to hdr_len per frame */ > > > > > > > > > UAPI changes need to be added to the virtio spec. > > > Pls get this approved by the virtio TC. > > > Thanks! > > > > There were some discussions last October in [email protected] > > mailing list. > > > That's it I could not find it. Could you include the archive link pls?
The email thread I found is https://yhbt.net/lore/all/[email protected]/T/#m62dd5e559a68e8d3e5872e85d37c924f65fc7033 There were discussions about updating the documents of SKB_GSO_TCP_ECN and SKB_GSO_TCP_ACCECN, and you can find it in the first patch of this series. > > > > At that moment, it is suggested to make Linux kernel accept new comments > > for SKB_GSO_TCP_ECN and SKB_GSO_TCP_ACCECN first. > > So, could virtio-spec colleague give your feedback? (Parav?). > > > > Otherwise, the CWR handling of virtio will be wrong after all Accurate ECN > > commits are merged in Linux. > > > > Chia-Yu > > if there's a general agreement we don't need to block linux on tc approval. > > -- > MST Shall I also submit patches to virtio-spec? Please suggest ways forwards. Thanks! Chia-Yu
