i40e/i40evf: Limit TSO to 7 descriptors for payload instead of 8 per packet

Orabug: 23176970

This patch addresses a bug introduced based on my interpretation of the
XL710 datasheet.  Specifically section 8.4.1 states that "A single transmit
packet may span up to 8 buffers (up to 8 data descriptors per packet
including both the header and payload buffers)."  It then later goes on to
say that each segment for a TSO obeys the previous rule, however it then
refers to TSO header and the segment payload buffers.

I believe the actual limit for fragments with TSO and a skbuff that has
payload data in the header portion of the buffer is actually only 7
fragments as the skb->data portion counts as 2 buffers, one for the TSO
header, and one for a segment payload buffer.

Fixes: 2d37490b82af ("i40e/i40evf: Rewrite logic for 8 descriptor per packet check")
Reported-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Acked-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
(cherry picked from commit 3f3f7cb875c0f621485644d4fd7453b0d37f00e4)
Signed-off-by: Brian Maly <brian.maly@oracle.com>

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index c6c5f3810ee3b02c179efad9baa46bf533b1244c..ea7fb2c6bb98245c869dc22da31e8f7b3daee301 100644 (file)
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -2593,35 +2593,34 @@ 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
+ * __i40e_chk_linearize - Check if there are more than 8 buffers per packet
  * @skb:      send buffer
  *
- * 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.
+ * Note: Our HW can't DMA more than 8 buffers to build a packet on the wire
+ * and so we need to figure out the cases where we need to linearize the skb.
+ *
+ * For TSO we need to count the TSO header and segment payload separately.
+ * As such we need to check cases where we have 7 fragments or more as we
+ * can potentially require 9 DMA transactions, 1 for the TSO header, 1 for
+ * the segment payload in the first descriptor, and another 7 for the
+ * fragments.
  **/
 bool __i40e_chk_linearize(struct sk_buff *skb)
 {
        const struct skb_frag_struct *frag, *stale;
-       int gso_size, nr_frags, sum;
-
-       /* check to see if TSO is enabled, if so we may get a repreive */
-       gso_size = skb_shinfo(skb)->gso_size;
-       if (unlikely(!gso_size))
-               return true;
+       int nr_frags, sum;
 
-       /* no need to check if number of frags is less than 8 */
+       /* no need to check if number of frags is less than 7 */
        nr_frags = skb_shinfo(skb)->nr_frags;
-       if (nr_frags < I40E_MAX_BUFFER_TXD)
+       if (nr_frags < (I40E_MAX_BUFFER_TXD - 1))
                return false;
 
        /* We need to walk through the list and validate that each group
         * of 6 fragments totals at least gso_size.  However we don't need
-        * to perform such validation on the first or last 6 since the first
-        * 6 cannot inherit any data from a descriptor before them, and the
-        * last 6 cannot inherit any data from a descriptor after them.
+        * to perform such validation on the last 6 since the last 6 cannot
+        * inherit any data from a descriptor after them.
         */
-       nr_frags -= I40E_MAX_BUFFER_TXD - 1;
+       nr_frags -= I40E_MAX_BUFFER_TXD - 2;
        frag = &skb_shinfo(skb)->frags[0];
 
        /* Initialize size to the negative value of gso_size minus 1.  We
@@ -2630,21 +2629,21 @@ bool __i40e_chk_linearize(struct sk_buff *skb)
         * descriptors for a single transmit as the header and previous
         * fragment are already consuming 2 descriptors.
         */
-       sum = 1 - gso_size;
+       sum = 1 - skb_shinfo(skb)->gso_size;
 
-       /* Add size of frags 1 through 5 to create our initial sum */
-       sum += skb_frag_size(++frag);
-       sum += skb_frag_size(++frag);
-       sum += skb_frag_size(++frag);
-       sum += skb_frag_size(++frag);
-       sum += skb_frag_size(++frag);
+       /* Add size of frags 0 through 4 to create our initial sum */
+       sum += skb_frag_size(frag++);
+       sum += skb_frag_size(frag++);
+       sum += skb_frag_size(frag++);
+       sum += skb_frag_size(frag++);
+       sum += skb_frag_size(frag++);
 
        /* Walk through fragments adding latest fragment, testing it, and
         * then removing stale fragments from the sum.
         */
        stale = &skb_shinfo(skb)->frags[0];
        for (;;) {
-               sum += skb_frag_size(++frag);
+               sum += skb_frag_size(frag++);
 
                /* if sum is negative we failed to make sufficient progress */
                if (sum < 0)
@@ -2654,7 +2653,7 @@ bool __i40e_chk_linearize(struct sk_buff *skb)
                if (!--nr_frags)
                        break;
 
-               sum -= skb_frag_size(++stale);
+               sum -= skb_frag_size(stale++);
        }
 
        return false;

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.h b/drivers/net/ethernet/intel/i40e/i40e_txrx.h
index cdd5dc00aec519972dd3af6166666a0d3c65766f..a9bd70537d6547b550a591b7775a8fcf4c76f186 100644 (file)
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.h
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.h
@@ -413,10 +413,14 @@ static inline int i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
  **/
 static inline bool i40e_chk_linearize(struct sk_buff *skb, int count)
 {
-       /* we can only support up to 8 data buffers for a single send */
-       if (likely(count <= I40E_MAX_BUFFER_TXD))
+       /* Both TSO and single send will work if count is less than 8 */
+       if (likely(count < I40E_MAX_BUFFER_TXD))
                return false;
 
-       return __i40e_chk_linearize(skb);
+       if (skb_is_gso(skb))
+               return __i40e_chk_linearize(skb);
+
+       /* we can support up to 8 data buffers for a single send */
+       return count != I40E_MAX_BUFFER_TXD;
 }
 #endif /* _I40E_TXRX_H_ */

diff --git a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
index 5314534ad5d80aeb60fefc090b2ea63978bceb19..d669c57fcb7a7a1eb00734b01098564f65178f3e 100644 (file)
--- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
@@ -1795,35 +1795,34 @@ static void i40e_create_tx_ctx(struct i40e_ring *tx_ring,
 }
 
 /**
- * __i40evf_chk_linearize - Check if there are more than 8 fragments per packet
+ * __i40evf_chk_linearize - Check if there are more than 8 buffers per packet
  * @skb:      send buffer
  *
- * 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.
+ * Note: Our HW can't DMA more than 8 buffers to build a packet on the wire
+ * and so we need to figure out the cases where we need to linearize the skb.
+ *
+ * For TSO we need to count the TSO header and segment payload separately.
+ * As such we need to check cases where we have 7 fragments or more as we
+ * can potentially require 9 DMA transactions, 1 for the TSO header, 1 for
+ * the segment payload in the first descriptor, and another 7 for the
+ * fragments.
  **/
 bool __i40evf_chk_linearize(struct sk_buff *skb)
 {
        const struct skb_frag_struct *frag, *stale;
-       int gso_size, nr_frags, sum;
-
-       /* check to see if TSO is enabled, if so we may get a repreive */
-       gso_size = skb_shinfo(skb)->gso_size;
-       if (unlikely(!gso_size))
-               return true;
+       int nr_frags, sum;
 
-       /* no need to check if number of frags is less than 8 */
+       /* no need to check if number of frags is less than 7 */
        nr_frags = skb_shinfo(skb)->nr_frags;
-       if (nr_frags < I40E_MAX_BUFFER_TXD)
+       if (nr_frags < (I40E_MAX_BUFFER_TXD - 1))
                return false;
 
        /* We need to walk through the list and validate that each group
         * of 6 fragments totals at least gso_size.  However we don't need
-        * to perform such validation on the first or last 6 since the first
-        * 6 cannot inherit any data from a descriptor before them, and the
-        * last 6 cannot inherit any data from a descriptor after them.
+        * to perform such validation on the last 6 since the last 6 cannot
+        * inherit any data from a descriptor after them.
         */
-       nr_frags -= I40E_MAX_BUFFER_TXD - 1;
+       nr_frags -= I40E_MAX_BUFFER_TXD - 2;
        frag = &skb_shinfo(skb)->frags[0];
 
        /* Initialize size to the negative value of gso_size minus 1.  We
@@ -1832,21 +1831,21 @@ bool __i40evf_chk_linearize(struct sk_buff *skb)
         * descriptors for a single transmit as the header and previous
         * fragment are already consuming 2 descriptors.
         */
-       sum = 1 - gso_size;
+       sum = 1 - skb_shinfo(skb)->gso_size;
 
-       /* Add size of frags 1 through 5 to create our initial sum */
-       sum += skb_frag_size(++frag);
-       sum += skb_frag_size(++frag);
-       sum += skb_frag_size(++frag);
-       sum += skb_frag_size(++frag);
-       sum += skb_frag_size(++frag);
+       /* Add size of frags 0 through 4 to create our initial sum */
+       sum += skb_frag_size(frag++);
+       sum += skb_frag_size(frag++);
+       sum += skb_frag_size(frag++);
+       sum += skb_frag_size(frag++);
+       sum += skb_frag_size(frag++);
 
        /* Walk through fragments adding latest fragment, testing it, and
         * then removing stale fragments from the sum.
         */
        stale = &skb_shinfo(skb)->frags[0];
        for (;;) {
-               sum += skb_frag_size(++frag);
+               sum += skb_frag_size(frag++);
 
                /* if sum is negative we failed to make sufficient progress */
                if (sum < 0)
@@ -1856,7 +1855,7 @@ bool __i40evf_chk_linearize(struct sk_buff *skb)
                if (!--nr_frags)
                        break;
 
-               sum -= skb_frag_size(++stale);
+               sum -= skb_frag_size(stale++);
        }
 
        return false;

diff --git a/drivers/net/ethernet/intel/i40evf/i40e_txrx.h b/drivers/net/ethernet/intel/i40evf/i40e_txrx.h
index c1dd8c5c966697bc79ae47babbab8a598d20ef18..0429553fe8870cb7f38ae07ab13bb0c94d07dbe0 100644 (file)
--- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.h
+++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.h
@@ -395,10 +395,14 @@ static inline int i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
  **/
 static inline bool i40e_chk_linearize(struct sk_buff *skb, int count)
 {
-       /* we can only support up to 8 data buffers for a single send */
-       if (likely(count <= I40E_MAX_BUFFER_TXD))
+       /* Both TSO and single send will work if count is less than 8 */
+       if (likely(count < I40E_MAX_BUFFER_TXD))
                return false;
 
-       return __i40evf_chk_linearize(skb);
+       if (skb_is_gso(skb))
+               return __i40evf_chk_linearize(skb);
+
+       /* we can support up to 8 data buffers for a single send */
+       return count != I40E_MAX_BUFFER_TXD;
 }
 #endif /* _I40E_TXRX_H_ */