i40e: Fix TSO with more than 8 frags per segment issue

The hardware has some limitations the driver needs to adhere to,
that we found in extended testing.
  1) no more than 8 descriptors per packet on the wire
  2) no header can span more than 3 descriptors

If one of these events occurs, the hardware will generate an internal
error and freeze the Tx queue.

This patch linearizes the skb to avoid these situations.

Change-ID: I37dab7d3966e14895a9663ec4d0aaa8eb0d9e115
Signed-off-by: Anjali Singhai Jain <anjali.singhai@intel.com>
Tested-by: Jim Young <james.m.young@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index 2206d2d..0aad611 100644 (file)
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -2140,6 +2140,67 @@ static int i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
 }
 
 /**
+ * i40e_chk_linearize - Check if there are more than 8 fragments per packet
+ * @skb:      send buffer
+ * @tx_flags: collected send information
+ * @hdr_len:  size of the packet header
+ *
+ * Note: Our HW can't scatter-gather more than 8 fragments to build
+ * a packet on the wire and so we need to figure out the cases where we
+ * need to linearize the skb.
+ **/
+static bool i40e_chk_linearize(struct sk_buff *skb, u32 tx_flags,
+                              const u8 hdr_len)
+{
+       struct skb_frag_struct *frag;
+       bool linearize = false;
+       unsigned int size = 0;
+       u16 num_frags;
+       u16 gso_segs;
+
+       num_frags = skb_shinfo(skb)->nr_frags;
+       gso_segs = skb_shinfo(skb)->gso_segs;
+
+       if (tx_flags & (I40E_TX_FLAGS_TSO | I40E_TX_FLAGS_FSO)) {
+               u16 j = 1;
+
+               if (num_frags < (I40E_MAX_BUFFER_TXD))
+                       goto linearize_chk_done;
+               /* try the simple math, if we have too many frags per segment */
+               if (DIV_ROUND_UP((num_frags + gso_segs), gso_segs) >
+                   I40E_MAX_BUFFER_TXD) {
+                       linearize = true;
+                       goto linearize_chk_done;
+               }
+               frag = &skb_shinfo(skb)->frags[0];
+               size = hdr_len;
+               /* we might still have more fragments per segment */
+               do {
+                       size += skb_frag_size(frag);
+                       frag++; j++;
+                       if (j == I40E_MAX_BUFFER_TXD) {
+                               if (size < skb_shinfo(skb)->gso_size) {
+                                       linearize = true;
+                                       break;
+                               }
+                               j = 1;
+                               size -= skb_shinfo(skb)->gso_size;
+                               if (size)
+                                       j++;
+                               size += hdr_len;
+                       }
+                       num_frags--;
+               } while (num_frags);
+       } else {
+               if (num_frags >= I40E_MAX_BUFFER_TXD)
+                       linearize = true;
+       }
+
+linearize_chk_done:
+       return linearize;
+}
+
+/**
  * i40e_tx_map - Build the Tx descriptor
  * @tx_ring:  ring to send buffer on
  * @skb:      send buffer
@@ -2396,6 +2457,10 @@ static netdev_tx_t i40e_xmit_frame_ring(struct sk_buff *skb,
        if (tsyn)
                tx_flags |= I40E_TX_FLAGS_TSYN;
 
+       if (i40e_chk_linearize(skb, tx_flags, hdr_len))
+               if (skb_linearize(skb))
+                       goto out_drop;
+
        skb_tx_timestamp(skb);
 
        /* always enable CRC insertion offload */

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.h b/drivers/net/ethernet/intel/i40e/i40e_txrx.h
index 18b0023..dff0bae 100644 (file)
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.h
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.h
@@ -112,6 +112,7 @@ enum i40e_dyn_idx_t {
 
 #define i40e_rx_desc i40e_32byte_rx_desc
 
+#define I40E_MAX_BUFFER_TXD    8
 #define I40E_MIN_TX_LEN                17
 #define I40E_MAX_DATA_PER_TXD  8192
 

diff --git a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
index 2900438..1320a43 100644 (file)
--- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
@@ -1380,6 +1380,67 @@ static void i40e_create_tx_ctx(struct i40e_ring *tx_ring,
        context_desc->type_cmd_tso_mss = cpu_to_le64(cd_type_cmd_tso_mss);
 }
 
+ /**
+ * i40e_chk_linearize - Check if there are more than 8 fragments per packet
+ * @skb:      send buffer
+ * @tx_flags: collected send information
+ * @hdr_len:  size of the packet header
+ *
+ * Note: Our HW can't scatter-gather more than 8 fragments to build
+ * a packet on the wire and so we need to figure out the cases where we
+ * need to linearize the skb.
+ **/
+static bool i40e_chk_linearize(struct sk_buff *skb, u32 tx_flags,
+                              const u8 hdr_len)
+{
+       struct skb_frag_struct *frag;
+       bool linearize = false;
+       unsigned int size = 0;
+       u16 num_frags;
+       u16 gso_segs;
+
+       num_frags = skb_shinfo(skb)->nr_frags;
+       gso_segs = skb_shinfo(skb)->gso_segs;
+
+       if (tx_flags & (I40E_TX_FLAGS_TSO | I40E_TX_FLAGS_FSO)) {
+               u16 j = 1;
+
+               if (num_frags < (I40E_MAX_BUFFER_TXD))
+                       goto linearize_chk_done;
+               /* try the simple math, if we have too many frags per segment */
+               if (DIV_ROUND_UP((num_frags + gso_segs), gso_segs) >
+                   I40E_MAX_BUFFER_TXD) {
+                       linearize = true;
+                       goto linearize_chk_done;
+               }
+               frag = &skb_shinfo(skb)->frags[0];
+               size = hdr_len;
+               /* we might still have more fragments per segment */
+               do {
+                       size += skb_frag_size(frag);
+                       frag++; j++;
+                       if (j == I40E_MAX_BUFFER_TXD) {
+                               if (size < skb_shinfo(skb)->gso_size) {
+                                       linearize = true;
+                                       break;
+                               }
+                               j = 1;
+                               size -= skb_shinfo(skb)->gso_size;
+                               if (size)
+                                       j++;
+                               size += hdr_len;
+                       }
+                       num_frags--;
+               } while (num_frags);
+       } else {
+               if (num_frags >= I40E_MAX_BUFFER_TXD)
+                       linearize = true;
+       }
+
+linearize_chk_done:
+       return linearize;
+}
+
 /**
  * i40e_tx_map - Build the Tx descriptor
  * @tx_ring:  ring to send buffer on
@@ -1654,6 +1715,10 @@ static netdev_tx_t i40e_xmit_frame_ring(struct sk_buff *skb,
        else if (tso)
                tx_flags |= I40E_TX_FLAGS_TSO;
 
+       if (i40e_chk_linearize(skb, tx_flags, hdr_len))
+               if (skb_linearize(skb))
+                       goto out_drop;
+
        skb_tx_timestamp(skb);
 
        /* always enable CRC insertion offload */

diff --git a/drivers/net/ethernet/intel/i40evf/i40e_txrx.h b/drivers/net/ethernet/intel/i40evf/i40e_txrx.h
index 4e15903..c950a03 100644 (file)
--- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.h
+++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.h
@@ -112,6 +112,7 @@ enum i40e_dyn_idx_t {
 
 #define i40e_rx_desc i40e_32byte_rx_desc
 
+#define I40E_MAX_BUFFER_TXD    8
 #define I40E_MIN_TX_LEN                17
 #define I40E_MAX_DATA_PER_TXD  8192