iw_cxgb4: Choose appropriate hw mtu index and ISS for iWARP connections

Select the appropriate hw mtu index and initial sequence number to optimize
hw memory performance.

Add new cxgb4_best_aligned_mtu() which allows callers to provide enough
information to be used to [possibly] select an MTU which will result in the
TCP Data Segment Size (AKA Maximum Segment Size) to be an aligned value.

If an RTR message exhange is required, then align the ISS to 8B - 1 + 4, so
that after the SYN the send seqno will align on a 4B boundary. The RTR
message exchange will leave the send seqno aligned on an 8B boundary.
If an RTR is not required, then align the ISS to 8B - 1.  The goal is
to have the send seqno be 8B aligned when we send the first FPDU.

Based on original work by Casey Leedom <leeedom@chelsio.com> and
Steve Wise <swise@opengridcomputing.com>

Signed-off-by: Casey Leedom <leedom@chelsio.com>
Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 63 insertions, 11 deletions

diff --git a/drivers/infiniband/hw/cxgb4/cm.c b/drivers/infiniband/hw/cxgb4/cm.c
index 1f863a96a480..d2e9f72ec9bf 100644
--- a/drivers/infiniband/hw/cxgb4/cm.c
+++ b/drivers/infiniband/hw/cxgb4/cm.c
@@ -232,12 +232,16 @@ static void release_tid(struct c4iw_rdev *rdev, u32 hwtid, struct sk_buff *skb)
 
 static void set_emss(struct c4iw_ep *ep, u16 opt)
 {
-        ep->emss = ep->com.dev->rdev.lldi.mtus[GET_TCPOPT_MSS(opt)] - 40;
+        ep->emss = ep->com.dev->rdev.lldi.mtus[GET_TCPOPT_MSS(opt)] -
+                   sizeof(struct iphdr) - sizeof(struct tcphdr);
         ep->mss = ep->emss;
         if (GET_TCPOPT_TSTAMP(opt))
                 ep->emss -= 12;
         if (ep->emss < 128)
                 ep->emss = 128;
+        if (ep->emss & 7)
+                PDBG("Warning: misaligned mtu idx %u mss %u emss=%u\n",
+                     GET_TCPOPT_MSS(opt), ep->mss, ep->emss);
         PDBG("%s mss_idx %u mss %u emss=%u\n", __func__, GET_TCPOPT_MSS(opt),
              ep->mss, ep->emss);
 }
@@ -528,6 +532,17 @@ static int send_abort(struct c4iw_ep *ep, struct sk_buff *skb, gfp_t gfp)
         return c4iw_l2t_send(&ep->com.dev->rdev, skb, ep->l2t);
 }
 
+static void best_mtu(const unsigned short *mtus, unsigned short mtu,
+                     unsigned int *idx, int use_ts)
+{
+        unsigned short hdr_size = sizeof(struct iphdr) +
+                                  sizeof(struct tcphdr) +
+                                  (use_ts ? 12 : 0);
+        unsigned short data_size = mtu - hdr_size;
+
+        cxgb4_best_aligned_mtu(mtus, hdr_size, data_size, 8, idx);
+}
+
 static int send_connect(struct c4iw_ep *ep)
 {
         struct cpl_act_open_req *req;
@@ -565,7 +580,8 @@ static int send_connect(struct c4iw_ep *ep)
         }
         set_wr_txq(skb, CPL_PRIORITY_SETUP, ep->ctrlq_idx);
 
-        cxgb4_best_mtu(ep->com.dev->rdev.lldi.mtus, ep->mtu, &mtu_idx);
+        best_mtu(ep->com.dev->rdev.lldi.mtus, ep->mtu, &mtu_idx,
+                 enable_tcp_timestamps);
         wscale = compute_wscale(rcv_win);
         opt0 = (nocong ? NO_CONG(1) : 0) |
                KEEP_ALIVE(1) |
@@ -633,6 +649,13 @@ static int send_connect(struct c4iw_ep *ep)
                         req6->opt2 = cpu_to_be32(opt2);
                 }
         } else {
+                u32 isn = (prandom_u32() & ~7UL) - 1;
+
+                opt2 |= T5_OPT_2_VALID;
+                opt2 |= CONG_CNTRL_VALID; /* OPT_2_ISS for T5 */
+                if (peer2peer)
+                        isn += 4;
+
                 if (ep->com.remote_addr.ss_family == AF_INET) {
                         t5_req = (struct cpl_t5_act_open_req *)
                                  skb_put(skb, wrlen);
@@ -649,6 +672,9 @@ static int send_connect(struct c4iw_ep *ep)
                                                      cxgb4_select_ntuple(
                                              ep->com.dev->rdev.lldi.ports[0],
                                              ep->l2t)));
+                        t5_req->rsvd = cpu_to_be32(isn);
+                        PDBG("%s snd_isn %u\n", __func__,
+                             be32_to_cpu(t5_req->rsvd));
                         t5_req->opt2 = cpu_to_be32(opt2);
                 } else {
                         t5_req6 = (struct cpl_t5_act_open_req6 *)
@@ -672,6 +698,9 @@ static int send_connect(struct c4iw_ep *ep)
                                                         cxgb4_select_ntuple(
                                                 ep->com.dev->rdev.lldi.ports[0],
                                                 ep->l2t));
+                        t5_req6->rsvd = cpu_to_be32(isn);
+                        PDBG("%s snd_isn %u\n", __func__,
+                             be32_to_cpu(t5_req6->rsvd));
                         t5_req6->opt2 = cpu_to_be32(opt2);
                 }
         }
@@ -1640,7 +1669,8 @@ static void send_fw_act_open_req(struct c4iw_ep *ep, unsigned int atid)
                         htons(F_FW_OFLD_CONNECTION_WR_CPLRXDATAACK);
         req->tcb.tx_max = (__force __be32) jiffies;
         req->tcb.rcv_adv = htons(1);
-        cxgb4_best_mtu(ep->com.dev->rdev.lldi.mtus, ep->mtu, &mtu_idx);
+        best_mtu(ep->com.dev->rdev.lldi.mtus, ep->mtu, &mtu_idx,
+                 enable_tcp_timestamps);
         wscale = compute_wscale(rcv_win);
         req->tcb.opt0 = (__force __be64) (TCAM_BYPASS(1) |
                 (nocong ? NO_CONG(1) : 0) |
@@ -1986,12 +2016,26 @@ static void accept_cr(struct c4iw_ep *ep, struct sk_buff *skb,
         u64 opt0;
         u32 opt2;
         int wscale;
+        struct cpl_t5_pass_accept_rpl *rpl5 = NULL;
 
         PDBG("%s ep %p tid %u\n", __func__, ep, ep->hwtid);
         BUG_ON(skb_cloned(skb));
-        skb_trim(skb, sizeof(*rpl));
+
         skb_get(skb);
-        cxgb4_best_mtu(ep->com.dev->rdev.lldi.mtus, ep->mtu, &mtu_idx);
+        rpl = cplhdr(skb);
+        if (is_t5(ep->com.dev->rdev.lldi.adapter_type)) {
+                skb_trim(skb, roundup(sizeof(*rpl5), 16));
+                rpl5 = (void *)rpl;
+                INIT_TP_WR(rpl5, ep->hwtid);
+        } else {
+                skb_trim(skb, sizeof(*rpl));
+                INIT_TP_WR(rpl, ep->hwtid);
+        }
+        OPCODE_TID(rpl) = cpu_to_be32(MK_OPCODE_TID(CPL_PASS_ACCEPT_RPL,
+                                                    ep->hwtid));
+
+        best_mtu(ep->com.dev->rdev.lldi.mtus, ep->mtu, &mtu_idx,
+                 enable_tcp_timestamps && req->tcpopt.tstamp);
         wscale = compute_wscale(rcv_win);
         opt0 = (nocong ? NO_CONG(1) : 0) |
                KEEP_ALIVE(1) |
@@ -2023,14 +2067,18 @@ static void accept_cr(struct c4iw_ep *ep, struct sk_buff *skb,
                         opt2 |= CCTRL_ECN(1);
         }
         if (is_t5(ep->com.dev->rdev.lldi.adapter_type)) {
+                u32 isn = (prandom_u32() & ~7UL) - 1;
                 opt2 |= T5_OPT_2_VALID;
                 opt2 |= V_CONG_CNTRL(CONG_ALG_TAHOE);
+                opt2 |= CONG_CNTRL_VALID; /* OPT_2_ISS for T5 */
+                rpl5 = (void *)rpl;
+                memset(&rpl5->iss, 0, roundup(sizeof(*rpl5)-sizeof(*rpl), 16));
+                if (peer2peer)
+                        isn += 4;
+                rpl5->iss = cpu_to_be32(isn);
+                PDBG("%s iss %u\n", __func__, be32_to_cpu(rpl5->iss));
         }
 
-        rpl = cplhdr(skb);
-        INIT_TP_WR(rpl, ep->hwtid);
-        OPCODE_TID(rpl) = cpu_to_be32(MK_OPCODE_TID(CPL_PASS_ACCEPT_RPL,
-                                      ep->hwtid));
         rpl->opt0 = cpu_to_be64(opt0);
         rpl->opt2 = cpu_to_be32(opt2);
         set_wr_txq(skb, CPL_PRIORITY_SETUP, ep->ctrlq_idx);
@@ -2095,6 +2143,7 @@ static int pass_accept_req(struct c4iw_dev *dev, struct sk_buff *skb)
         int err;
         u16 peer_mss = ntohs(req->tcpopt.mss);
         int iptype;
+        unsigned short hdrs;
 
         parent_ep = lookup_stid(t, stid);
         if (!parent_ep) {
@@ -2152,8 +2201,10 @@ static int pass_accept_req(struct c4iw_dev *dev, struct sk_buff *skb)
                 goto reject;
         }
 
-        if (peer_mss && child_ep->mtu > (peer_mss + 40))
-                child_ep->mtu = peer_mss + 40;
+        hdrs = sizeof(struct iphdr) + sizeof(struct tcphdr) +
+               ((enable_tcp_timestamps && req->tcpopt.tstamp) ? 12 : 0);
+        if (peer_mss && child_ep->mtu > (peer_mss + hdrs))
+                child_ep->mtu = peer_mss + hdrs;
 
         state_set(&child_ep->com, CONNECTING);
         child_ep->com.dev = dev;
diff --git a/drivers/infiniband/hw/cxgb4/t4fw_ri_api.h b/drivers/infiniband/hw/cxgb4/t4fw_ri_api.h
index 6121ca08fe58..91289a051af9 100644
--- a/drivers/infiniband/hw/cxgb4/t4fw_ri_api.h
+++ b/drivers/infiniband/hw/cxgb4/t4fw_ri_api.h
@@ -848,6 +848,7 @@ enum {                     /* TCP congestion control algorithms */
 #define V_CONG_CNTRL(x) ((x) << S_CONG_CNTRL)
 #define G_CONG_CNTRL(x) (((x) >> S_CONG_CNTRL) & M_CONG_CNTRL)
 
+#define CONG_CNTRL_VALID   (1 << 18)
 #define T5_OPT_2_VALID       (1 << 31)
 
 #endif /* _T4FW_RI_API_H_ */