Re: [dpdk-dev] [PATCH v3 8/8] examples/vhost:support TX offload in vhost sample

["Liu, Jijiang" <jijiang.liu@intel.com>]

> -----Original Message-----
> From: Yuanhan Liu [mailto:yuanhan.liu@linux.intel.com]
> Sent: Monday, November 09, 2015 12:17 PM
> To: Liu, Jijiang
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v3 8/8] examples/vhost:support TX offload in
> vhost sample
> 
> On Wed, Nov 04, 2015 at 06:54:16PM +0800, Jijiang Liu wrote:
> > Change the vhost sample to support and test TX offload.
> >
> > Signed-off-by: Jijiang Liu <jijiang.liu@intel.com>
> > ---
> >  examples/vhost/main.c |  128
> > ++++++++++++++++++++++++++++++++++++++++++-------
> >  1 files changed, 111 insertions(+), 17 deletions(-)
> >
> > diff --git a/examples/vhost/main.c b/examples/vhost/main.c index
> > 9eac2d0..06e1e8b 100644
> > --- a/examples/vhost/main.c
> > +++ b/examples/vhost/main.c
> > @@ -50,6 +50,10 @@
> >  #include <rte_string_fns.h>
> >  #include <rte_malloc.h>
> >  #include <rte_virtio_net.h>
> > +#include <rte_tcp.h>
> > +#include <rte_ip.h>
> > +#include <rte_udp.h>
> > +#include <rte_sctp.h>
> >
> >  #include "main.h"
> >
> > @@ -140,6 +144,8 @@
> >
> >  #define MBUF_EXT_MEM(mb)   (rte_mbuf_from_indirect(mb) != (mb))
> >
> > +#define VIRTIO_TX_CKSUM_OFFLOAD_MASK (PKT_TX_IP_CKSUM |
> > +PKT_TX_L4_MASK)
> > +
> >  /* mask of enabled ports */
> >  static uint32_t enabled_port_mask = 0;
> >
> > @@ -197,6 +203,13 @@ typedef enum {
> >  static uint32_t enable_stats = 0;
> >  /* Enable retries on RX. */
> >  static uint32_t enable_retry = 1;
> > +
> > +/* Disable TX checksum offload */
>       ^^^^^^^
> You meant to "Enable"?
> 
> > +static uint32_t enable_tx_csum;
> > +
> > +/* Disable TSO offload */
> > +static uint32_t enable_tso;
> 
> Actually, I'd like to see TSO/CSUM offloading is enabled by default:
> they are so common, and they are enabled in a lot places by default, say,
> kernel, qemu. There is no reason to make it "disable" here.
> 
> > +
> >  /* Specify timeout (in useconds) between retries on RX. */  static
> > uint32_t burst_rx_delay_time = BURST_RX_WAIT_US;
> >  /* Specify the number of retries on RX. */ @@ -292,20 +305,6 @@
> > struct vlan_ethhdr {
> >  	__be16          h_vlan_encapsulated_proto;
> >  };
> >
> > -/* IPv4 Header */
> > -struct ipv4_hdr {
> > -	uint8_t  version_ihl;		/**< version and header length */
> > -	uint8_t  type_of_service;	/**< type of service */
> > -	uint16_t total_length;		/**< length of packet */
> > -	uint16_t packet_id;		/**< packet ID */
> > -	uint16_t fragment_offset;	/**< fragmentation offset */
> > -	uint8_t  time_to_live;		/**< time to live */
> > -	uint8_t  next_proto_id;		/**< protocol ID */
> > -	uint16_t hdr_checksum;		/**< header checksum */
> > -	uint32_t src_addr;		/**< source address */
> > -	uint32_t dst_addr;		/**< destination address */
> > -} __attribute__((__packed__));
> 
> 
> Minor nit: it's a cleanup, having nothing to do with this patch (to
> demonstrate TSO/CSUM). It belongs to another patch.
> 
> > -
> >  /* Header lengths. */
> >  #define VLAN_HLEN       4
> >  #define VLAN_ETH_HLEN   18
> > @@ -441,6 +440,14 @@ port_init(uint8_t port)
> >
> >  	if (port >= rte_eth_dev_count()) return -1;
> >
> > +	if (enable_tx_csum == 0)
> > +		rte_vhost_feature_disable(1ULL << VIRTIO_NET_F_CSUM);
> > +
> > +	if (enable_tso == 0) {
> > +		rte_vhost_feature_disable(1ULL <<
> VIRTIO_NET_F_HOST_TSO4);
> > +		rte_vhost_feature_disable(1ULL <<
> VIRTIO_NET_F_HOST_TSO6);
> > +	}
> > +
> >  	rx_rings = (uint16_t)dev_info.max_rx_queues;
> >  	/* Configure ethernet device. */
> >  	retval = rte_eth_dev_configure(port, rx_rings, tx_rings,
> > &port_conf); @@ -576,7 +583,9 @@ us_vhost_usage(const char
> *prgname)
> >  	"		--rx-desc-num [0-N]: the number of descriptors on rx,
> "
> >  			"used only when zero copy is enabled.\n"
> >  	"		--tx-desc-num [0-N]: the number of descriptors on tx,
> "
> > -			"used only when zero copy is enabled.\n",
> > +			"used only when zero copy is enabled.\n"
> > +	"		--tx-csum [0|1] disable/enable TX checksum
> offload.\n"
> > +	"		--tso [0|1] disable/enable TCP segement offload.\n",
> >  	       prgname);
> >  }
> >
> > @@ -602,6 +611,8 @@ us_vhost_parse_args(int argc, char **argv)
> >  		{"zero-copy", required_argument, NULL, 0},
> >  		{"rx-desc-num", required_argument, NULL, 0},
> >  		{"tx-desc-num", required_argument, NULL, 0},
> > +		{"tx-csum", required_argument, NULL, 0},
> > +		{"tso", required_argument, NULL, 0},
> >  		{NULL, 0, 0, 0},
> >  	};
> >
> > @@ -656,6 +667,28 @@ us_vhost_parse_args(int argc, char **argv)
> >  				}
> >  			}
> >
> > +			/* Enable/disable TX checksum offload. */
> > +			if (!strncmp(long_option[option_index].name, "tx-
> csum", MAX_LONG_OPT_SZ)) {
> > +				ret = parse_num_opt(optarg, 1);
> > +				if (ret == -1) {
> > +					RTE_LOG(INFO, VHOST_CONFIG,
> "Invalid argument for tx-csum [0|1]\n");
> > +					us_vhost_usage(prgname);
> > +					return -1;
> > +				} else
> > +					enable_tx_csum = ret;
> > +			}
> > +
> > +			/* Enable/disable TSO offload. */
> > +			if (!strncmp(long_option[option_index].name, "tso",
> MAX_LONG_OPT_SZ)) {
> > +				ret = parse_num_opt(optarg, 1);
> > +				if (ret == -1) {
> > +					RTE_LOG(INFO, VHOST_CONFIG,
> "Invalid argument for tso [0|1]\n");
> > +					us_vhost_usage(prgname);
> > +					return -1;
> > +				} else
> > +					enable_tso = ret;
> > +			}
> > +
> >  			/* Specify the retries delay time (in useconds) on RX.
> */
> >  			if (!strncmp(long_option[option_index].name, "rx-
> retry-delay", MAX_LONG_OPT_SZ)) {
> >  				ret = parse_num_opt(optarg, INT32_MAX);
> @@ -1114,6 +1147,63 @@
> > find_local_dest(struct virtio_net *dev, struct rte_mbuf *m,
> >  	return 0;
> >  }
> >
> > +static uint16_t
> > +get_psd_sum(void *l3_hdr, uint64_t ol_flags) {
> > +	if (ol_flags & PKT_TX_IPV4)
> > +		return rte_ipv4_phdr_cksum(l3_hdr, ol_flags);
> > +	else /* assume ethertype == ETHER_TYPE_IPv6 */
> > +		return rte_ipv6_phdr_cksum(l3_hdr, ol_flags); }
> > +
> > +static void virtio_tx_offload(struct rte_mbuf *m) {
> > +	void *l3_hdr;
> > +	struct ipv4_hdr *ipv4_hdr = NULL;
> > +	struct tcp_hdr *tcp_hdr = NULL;
> > +	struct udp_hdr *udp_hdr = NULL;
> > +	struct sctp_hdr *sctp_hdr = NULL;
> > +	struct ether_hdr *eth_hdr = rte_pktmbuf_mtod(m, struct ether_hdr
> *);
> > +
> > +	l3_hdr = (char *)eth_hdr + m->l2_len;
> > +
> > +	if (m->ol_flags & PKT_TX_IPV4) {
> > +		ipv4_hdr = (struct ipv4_hdr *)l3_hdr;
> > +		if (m->ol_flags & PKT_TX_IP_CKSUM)
> > +			ipv4_hdr->hdr_checksum = 0;
> > +	}
> > +
> > +	if (m->ol_flags & PKT_TX_L4_MASK) {
> > +		switch (m->ol_flags & PKT_TX_L4_MASK) {
> > +		case PKT_TX_TCP_CKSUM:
> > +			tcp_hdr = (struct tcp_hdr *)
> > +					((char *)l3_hdr + m->l3_len);
> > +			tcp_hdr->cksum = get_psd_sum(l3_hdr, m->ol_flags);
> 
> I'm wondering that's necessary here (even for the data going through nic).
> AFAIK, the kernel sending the data will calculate pseudo checksum.
> 
> (I may be wrong; a simple validation could prove that)
>
After testing with combining TSO, these fileds need to be set.
> 	--yliu