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Subject: [RFC PATCH] virtio-spec: Introduce new Receive-Segment-Coalescing feature for guest
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.aspxA 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 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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