[dpdk-dev] [PATCH 6/7] net/virtio: Add MTU feature support

[Aaron Conole]

Maxime Coquelin <maxime.coquelin at redhat.com> writes:

> This patch implements support for the Virtio MTU feature.
> When negotiated, the host shares its maximum supported MTU,
> which is used as initial MTU and as maximum MTU the application
> can set.
>
> Signed-off-by: Maxime Coquelin <maxime.coquelin at redhat.com>
> ---
>  doc/guides/nics/features/virtio.ini |  1 +
>  drivers/net/virtio/virtio_ethdev.c  | 22 ++++++++++++++++++++--
>  drivers/net/virtio/virtio_ethdev.h  |  3 ++-
>  drivers/net/virtio/virtio_pci.h     |  3 +++
>  4 files changed, 26 insertions(+), 3 deletions(-)
>
> diff --git a/doc/guides/nics/features/virtio.ini b/doc/guides/nics/features/virtio.ini
> index 5164937..7bea075 100644
> --- a/doc/guides/nics/features/virtio.ini
> +++ b/doc/guides/nics/features/virtio.ini
> @@ -24,3 +24,4 @@ ARMv8                = Y
>  x86-32               = Y
>  x86-64               = Y
>  Usage doc            = Y
> +MTU update           = Y
> diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
> index d1ff234..ad3e6e1 100644
> --- a/drivers/net/virtio/virtio_ethdev.c
> +++ b/drivers/net/virtio/virtio_ethdev.c
> @@ -721,10 +721,13 @@ virtio_mtu_set(struct rte_eth_dev *dev, uint16_t mtu)
>  	uint32_t ether_hdr_len = ETHER_HDR_LEN + VLAN_TAG_LEN +
>  				 hw->vtnet_hdr_size;
>  	uint32_t frame_size = mtu + ether_hdr_len;
> +	uint32_t max_frame_size = hw->max_mtu + ether_hdr_len;
>  
> -	if (mtu < ETHER_MIN_MTU || frame_size > VIRTIO_MAX_RX_PKTLEN) {
> +	max_frame_size = RTE_MIN(max_frame_size, VIRTIO_MAX_RX_PKTLEN);
> +
> +	if (mtu < ETHER_MIN_MTU || frame_size > max_frame_size) {
>  		PMD_INIT_LOG(ERR, "MTU should be between %d and %d",
> -			ETHER_MIN_MTU, VIRTIO_MAX_RX_PKTLEN - ether_hdr_len);
> +			ETHER_MIN_MTU, max_frame_size - ether_hdr_len);
>  		return -EINVAL;
>  	}
>  	return 0;
> @@ -1392,6 +1395,21 @@ virtio_init_device(struct rte_eth_dev *eth_dev, uint64_t req_features)
>  
>  		hw->max_queue_pairs = config->max_virtqueue_pairs;
>  
> +		if (vtpci_with_feature(hw, VIRTIO_NET_F_MTU)) {
> +			vtpci_read_dev_config(hw,
> +				offsetof(struct virtio_net_config, mtu),
> +				&config->mtu,
> +				sizeof(config->mtu));

I think we need to check the value here against the min mtu, right?

> +			hw->max_mtu = config->mtu;
> +			/* Set initial MTU to maximum one supported by vhost */
> +			eth_dev->data->mtu = config->mtu;
> +
> +		} else {
> +			hw->max_mtu = VIRTIO_MAX_RX_PKTLEN - ETHER_HDR_LEN -
> +				VLAN_TAG_LEN - hw->vtnet_hdr_size;
> +		}
> +
>  		PMD_INIT_LOG(DEBUG, "config->max_virtqueue_pairs=%d",
>  				config->max_virtqueue_pairs);
>  		PMD_INIT_LOG(DEBUG, "config->status=%d", config->status);
> diff --git a/drivers/net/virtio/virtio_ethdev.h b/drivers/net/virtio/virtio_ethdev.h
> index 777a14b..aa78adc 100644
> --- a/drivers/net/virtio/virtio_ethdev.h
> +++ b/drivers/net/virtio/virtio_ethdev.h
> @@ -51,7 +51,7 @@
>  #define VIRTIO_MAX_TX_QUEUES 128U
>  #define VIRTIO_MAX_MAC_ADDRS 64
>  #define VIRTIO_MIN_RX_BUFSIZE 64
> -#define VIRTIO_MAX_RX_PKTLEN  9728
> +#define VIRTIO_MAX_RX_PKTLEN  9728U
>  
>  /* Features desired/implemented by this driver. */
>  #define VIRTIO_PMD_DEFAULT_GUEST_FEATURES	\
> @@ -66,6 +66,7 @@
>  	 1u << VIRTIO_NET_F_HOST_TSO4	  |	\
>  	 1u << VIRTIO_NET_F_HOST_TSO6	  |	\
>  	 1u << VIRTIO_NET_F_MRG_RXBUF	  |	\
> +	 1u << VIRTIO_NET_F_MTU	| \
>  	 1u << VIRTIO_RING_F_INDIRECT_DESC |    \
>  	 1ULL << VIRTIO_F_VERSION_1       |	\
>  	 1ULL << VIRTIO_F_IOMMU_PLATFORM)
> diff --git a/drivers/net/virtio/virtio_pci.h b/drivers/net/virtio/virtio_pci.h
> index 59e45c4..771f5b1 100644
> --- a/drivers/net/virtio/virtio_pci.h
> +++ b/drivers/net/virtio/virtio_pci.h
> @@ -106,6 +106,7 @@ struct virtnet_ctl;
>  /* The feature bitmap for virtio net */
>  #define VIRTIO_NET_F_CSUM	0	/* Host handles pkts w/ partial csum */
>  #define VIRTIO_NET_F_GUEST_CSUM	1	/* Guest handles pkts w/ partial csum */
> +#define VIRTIO_NET_F_MTU	3	/* Initial MTU advice. */
>  #define VIRTIO_NET_F_MAC	5	/* Host has given MAC address. */
>  #define VIRTIO_NET_F_GUEST_TSO4	7	/* Guest can handle TSOv4 in. */
>  #define VIRTIO_NET_F_GUEST_TSO6	8	/* Guest can handle TSOv6 in. */
> @@ -251,6 +252,7 @@ struct virtio_hw {
>  	uint64_t    req_guest_features;
>  	uint64_t    guest_features;
>  	uint32_t    max_queue_pairs;
> +	uint16_t	max_mtu;
>  	uint16_t    vtnet_hdr_size;
>  	uint8_t	    vlan_strip;
>  	uint8_t	    use_msix;
> @@ -296,6 +298,7 @@ struct virtio_net_config {
>  	/* See VIRTIO_NET_F_STATUS and VIRTIO_NET_S_* above */
>  	uint16_t   status;
>  	uint16_t   max_virtqueue_pairs;
> +	uint16_t   mtu;
>  } __attribute__((packed));
>  
>  /*