Re: [PATCH 2/3] virtio-net: Introduce RSS receive steering feature

From: Michael S. Tsirkin
Date: Sun Mar 01 2020 - 03:49:45 EST


On Sat, Feb 29, 2020 at 07:13:00PM +0200, Yuri Benditovich wrote:
> RSS (Receive-side scaling) defines hash calculation
> rules and decision on receive virtqueue according to
> the calculated hash, provided mask to apply and
> provided indirection table containing indices of
> receive virqueues. The driver sends the control
> command to enable multiqueue and provide parameters
> for receive steering.
>
> Signed-off-by: Yuri Benditovich <yuri.benditovich@xxxxxxxxxx>
> ---
> include/uapi/linux/virtio_net.h | 42 +++++++++++++++++++++++++++++++--
> 1 file changed, 40 insertions(+), 2 deletions(-)
>
> diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
> index 6e26a2cc6ad0..7a342657fb6c 100644
> --- a/include/uapi/linux/virtio_net.h
> +++ b/include/uapi/linux/virtio_net.h
> @@ -57,6 +57,7 @@
> * Steering */
> #define VIRTIO_NET_F_CTRL_MAC_ADDR 23 /* Set MAC address */
>
> +#define VIRTIO_NET_F_RSS 60 /* Supports RSS RX steering */
> #define VIRTIO_NET_F_RSC_EXT 61 /* extended coalescing info */
> #define VIRTIO_NET_F_STANDBY 62 /* Act as standby for another device
> * with the same MAC.
> @@ -70,6 +71,17 @@
> #define VIRTIO_NET_S_LINK_UP 1 /* Link is up */
> #define VIRTIO_NET_S_ANNOUNCE 2 /* Announcement is needed */
>
> +/* supported/enabled hash types */
> +#define VIRTIO_NET_RSS_HASH_TYPE_IPv4 (1 << 0)
> +#define VIRTIO_NET_RSS_HASH_TYPE_TCPv4 (1 << 1)
> +#define VIRTIO_NET_RSS_HASH_TYPE_UDPv4 (1 << 2)
> +#define VIRTIO_NET_RSS_HASH_TYPE_IPv6 (1 << 3)
> +#define VIRTIO_NET_RSS_HASH_TYPE_TCPv6 (1 << 4)
> +#define VIRTIO_NET_RSS_HASH_TYPE_UDPv6 (1 << 5)
> +#define VIRTIO_NET_RSS_HASH_TYPE_IP_EX (1 << 6)
> +#define VIRTIO_NET_RSS_HASH_TYPE_TCP_EX (1 << 7)
> +#define VIRTIO_NET_RSS_HASH_TYPE_UDP_EX (1 << 8)
> +
> struct virtio_net_config {
> /* The config defining mac address (if VIRTIO_NET_F_MAC) */
> __u8 mac[ETH_ALEN];
> @@ -93,6 +105,12 @@ struct virtio_net_config {
> * Any other value stands for unknown.
> */
> __u8 duplex;
> + /* maximal size of RSS key */
> + __u8 rss_max_key_size;
> + /* maximal number of indirection table entries */
> + __u16 rss_max_indirection_table_length;

This mirrors spec language. However I just stumbled upon this:

https://en.wikipedia.org/wiki/Maximal_and_minimal_elements

which seems to say maximal means "local maximum".
So I think we should fix both the spec and this header to
say "maximum" instead of "maximal".

Thanks!



> + /* bitmask of supported VIRTIO_NET_RSS_HASH_ types */
> + __u32 supported_hash_types;
> } __attribute__((packed));
>
> /*
> @@ -236,7 +254,9 @@ struct virtio_net_ctrl_mac {
>
> /*
> * Control Receive Flow Steering
> - *
> + */
> +#define VIRTIO_NET_CTRL_MQ 4
> +/*
> * The command VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET
> * enables Receive Flow Steering, specifying the number of the transmit and
> * receive queues that will be used. After the command is consumed and acked by
> @@ -249,11 +269,29 @@ struct virtio_net_ctrl_mq {
> __virtio16 virtqueue_pairs;
> };
>
> -#define VIRTIO_NET_CTRL_MQ 4
> #define VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET 0
> #define VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN 1
> #define VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX 0x8000
>
> +/*
> + * The command VIRTIO_NET_CTRL_MQ_RSS_CONFIG has the same effect as
> + * VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET does and additionally configures
> + * the receive steering to use a hash calculated for incoming packet
> + * to decide on receive virtqueue to place the packet. The command
> + * also provides parameters to calculate a hash and receive virtqueue.
> + */
> +struct virtio_net_rss_config {
> + __virtio32 hash_types;
> + __virtio16 indirection_table_mask;
> + __virtio16 unclassified_queue;
> + __virtio16 indirection_table[1/* + indirection_table_mask*/];
> + __virtio16 max_tx_vq;
> + __u8 hash_key_length;
> + __u8 hash_key_data[/*hash_key_length*/];
> +};


Should use __le and not __virtio.
__virtio is for legacy types which sometimes have variable endian-ness.


> +
> + #define VIRTIO_NET_CTRL_MQ_RSS_CONFIG 1
> +
> /*
> * Control network offloads
> *
> --
> 2.17.1