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Subject: Re: [RFC PATCH] virtio-spec: Introduce new Receive-Segment-Coalescing feature for guest
On Mon, Jun 06, 2016 at 05:27:12PM +0800, Wei Xu wrote: > Hi TCers, > Recently i'm working on a feature named as Receive-Segment-Coalescing for > userspace virtio-net, which is mainly aimed to support WHQL test case for > windows guest, the below link is the detailed information from microsoft. > > https://msdn.microsoft.com/en-us/library/windows/hardware/jj853323%28v=vs.85%29.aspx > > A new feature bit and a few new fields in virtio network header are > introduced to achieve this goal, please consider the request. > > Index: content.tex > =================================================================== > --- content.tex (revision 569) > +++ content.tex (working copy) > @@ -3086,6 +3086,11 @@ > > \item[VIRTIO_NET_F_CTRL_MAC_ADDR(23)] Set MAC address through control > channel. > + > +\item[VIRTIO_NET_F_GUEST_RSC4 (24)] Driver can receive coalesced ipv4 tcp > packets. > + > +\item[VIRTIO_NET_F_GUEST_RSC6 (25)] Driver can receive coalesced ipv6 tcp > packets. > + > \end{description} > > \subsubsection{Feature bit requirements}\label{sec:Device Types / Network 25 should not be used by devices. I suggest you use a high feature bit for this. How about bits 41 and 42? > Device / Feature bits / Feature bit requirements} > @@ -3247,8 +3252,11 @@ > u8 flags; > #define VIRTIO_NET_HDR_GSO_NONE 0 > #define VIRTIO_NET_HDR_GSO_TCPV4 1 > -#define VIRTIO_NET_HDR_GSO_UDP 3 > -#define VIRTIO_NET_HDR_GSO_TCPV6 4 > +#define VIRTIO_NET_HDR_GSO_UDP 2 > +#define VIRTIO_NET_HDR_GSO_TCPV6 3 > +#define VIRTIO_NET_HDR_RSC_NONE 4 > +#define VIRTIO_NET_HDR_RSC_TCPV4 5 > +#define VIRTIO_NET_HDR_RSC_TCPV6 6 > #define VIRTIO_NET_HDR_GSO_ECN 0x80 > u8 gso_type; > le16 hdr_len; > @@ -3256,6 +3264,9 @@ > le16 csum_start; > le16 csum_offset; > le16 num_buffers; > + le16 coalesced_pkts; > + le16 coalesced_size; > + le16 dup_acks; > }; > \end{lstlisting} > > @@ -3272,6 +3283,12 @@ > when VIRTIO_NET_F_MRG_RXBUF was negotiated; without that feature the > structure was 2 bytes shorter. > > +The legacy driver only presented \field{coalesced_pkts}, > \field{coalesced_size} > +and \field{dup_ack} in the struct virtio_net_hdr when > VIRTIO_NET_F_GUEST_RSC4 > +or VIRTIO_NET_F_GUEST_RSC6 was negotiated and a packet really has coalesced > +additional packet(s), without satisfying the 2 conditions the structure was > +6 bytes shorter. > + > When using the legacy interface, the driver SHOULD ignore the > \field{len} value in used ring entries for the transmit queues > and the controlq queue. > @@ -3451,6 +3468,19 @@ > 1514 bytes. The 12-byte struct virtio_net_hdr is prepended to this, > making for 65562 or 1526 bytes. > > +If the VIRTIO_NET_F_GUEST_RSC4 feature is used, the maximum incoming > +packet will be up to 65550 bytes long (the maximum size of a TCP packet, > +plus the 14 byte ethernet header), otherwise 1514 bytes. > +The 16-byte struct virtio_net_hdr is prepended to this, > +making for 65566 or 1528 bytes. > + > +If the VIRTIO_NET_F_GUEST_RSC6 feature is used, the maximum incoming > +packet will be up to 65590 bytes long (the maximum size of a TCP packet, > +plus the 40-byte standard ipv6 header, plus the 14 byte ethernet header), > +otherwise 1514 bytes. > +The 16-byte struct virtio_net_hdr is prepended to this, > +making for 65606 or 1528 bytes. > + > \drivernormative{\paragraph}{Setting Up Receive Buffers}{Device Types / > Network Device / Device Operation / Setting Up Receive Buffers} > > \begin{itemize} > @@ -3514,6 +3544,24 @@ > set: if so, device has validated the packet checksum. > In case of multiple encapsulated protocols, one level of checksums > has been validated. > + > +\item If one or both VIRTIO_NET_F_GUEST_RSC4, RSC6 were negotiated, > + but it is a original packet which didn't coalesce any packet, > + then the \field{flags} should be set to VIRTIO_NET_HDR_RSC_NONE. > + > +\item If the VIRTIO_NET_F_GUEST_RSC4, RSC6 options were negotiated, > + and \field{flags} notifies it's a coalesced packet, then > + \field{coalesced_pkts} indicates how many packets are coalesced into > + this packet. > + > +\item If the VIRTIO_NET_F_GUEST_RSC4, RSC6 options were negotiated, > + and \field{flags} notifies it's a coalesced packet, then > + \field{coalesced_size} indicates the real packet size after coalesced. > + > +\item If the VIRTIO_NET_F_GUEST_RSC4, RSC6 options were negotiated, > + and \field{flags} notifies it's a coalesced packet, then > + \field{dup_ack} indicates how many duplicated ack packets are > + coalesced into this packet. > \end{enumerate} > > Additionally, VIRTIO_NET_F_GUEST_CSUM, TSO4, TSO6, UDP and ECN > @@ -3626,6 +3674,15 @@ > If neither VIRTIO_NET_HDR_F_NEEDS_CSUM nor > VIRTIO_NET_HDR_F_DATA_VALID is set, the driver MUST NOT > rely on the packet checksum being correct. > + > +If one of VIRTIO_NET_F_GUEST_RSC4, RSC6 options have > +been negotiated, the driver MAY use \field{hdr_len} as a > +hint about the real virtio header size, for example, if a > +packets is an original packet, then the virtio header size > +should not contain the \field{coalesced_pkts}, \field{coalesced_size} > +and \field {dup_ack}, otherwise, these 3 fields should be included in > +virito header size. > + > \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / > Device Operation / Control Virtqueue} > > The driver uses the control virtqueue (if VIRTIO_NET_F_CTRL_VQ is
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