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Commit 3f3f7cb8 authored by Alexander Duyck's avatar Alexander Duyck Committed by Jeff Kirsher
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i40e/i40evf: Limit TSO to 7 descriptors for payload instead of 8 per packet 



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: 2d37490b ("i40e/i40evf: Rewrite logic for 8 descriptor per packet check")
Reported-by: default avatarSowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: default avatarAlexander Duyck <aduyck@mirantis.com>
Acked-by: default avatarJesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: default avatarSowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: default avatarJeff Kirsher <jeffrey.t.kirsher@intel.com>
parent a6d37131

drivers/net/ethernet/intel/i40e/i40e_txrx.c

+24 −25
Original line number Original line Diff line number Diff line
@@ -2594,35 +2594,34 @@ 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

 * @skb:      send buffer

 *

 *

 * Note: Our HW can't scatter-gather more than 8 fragments to build

 * Note: Our HW can't DMA more than 8 buffers to build a packet on the wire

 * a packet on the wire and so we need to figure out the cases where we

 * and so we need to figure out the cases where we need to linearize the skb.

 * 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)

bool __i40e_chk_linearize(struct sk_buff *skb)

{

{

	const struct skb_frag_struct *frag, *stale;

	const struct skb_frag_struct *frag, *stale;

	int gso_size, nr_frags, sum;

	int 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;





	/* 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;

	nr_frags = skb_shinfo(skb)->nr_frags;

	if (nr_frags < I40E_MAX_BUFFER_TXD)

	if (nr_frags < (I40E_MAX_BUFFER_TXD - 1))

		return false;

		return false;





	/* We need to walk through the list and validate that each group

	/* 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

	 * 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

	 * to perform such validation on the last 6 since the last 6 cannot

	 * 6 cannot inherit any data from a descriptor before them, and the

	 * inherit any data from a descriptor after them.

	 * 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];

	frag = &skb_shinfo(skb)->frags[0];





	/* Initialize size to the negative value of gso_size minus 1.  We

	/* Initialize size to the negative value of gso_size minus 1.  We
@@ -2631,21 +2630,21 @@ bool __i40e_chk_linearize(struct sk_buff *skb) 
	 * descriptors for a single transmit as the header and previous

	 * descriptors for a single transmit as the header and previous

	 * fragment are already consuming 2 descriptors.

	 * 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 */

	/* 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);

	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

	/* Walk through fragments adding latest fragment, testing it, and

	 * then removing stale fragments from the sum.

	 * then removing stale fragments from the sum.

	 */

	 */

	stale = &skb_shinfo(skb)->frags[0];

	stale = &skb_shinfo(skb)->frags[0];

	for (;;) {

	for (;;) {

		sum += skb_frag_size(++frag);

		sum += skb_frag_size(frag++);





		/* if sum is negative we failed to make sufficient progress */

		/* if sum is negative we failed to make sufficient progress */

		if (sum < 0)

		if (sum < 0)
@@ -2655,7 +2654,7 @@ bool __i40e_chk_linearize(struct sk_buff *skb) 
		if (!--nr_frags)

		if (!--nr_frags)

			break;

			break;





		sum -= skb_frag_size(++stale);

		sum -= skb_frag_size(stale++);

	}

	}





	return false;

	return false;

drivers/net/ethernet/intel/i40e/i40e_txrx.h

+7 −3
Original line number Original line Diff line number Diff line
@@ -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)

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 */

	/* Both TSO and single send will work if count is less than 8 */

	if (likely(count <= I40E_MAX_BUFFER_TXD))

	if (likely(count < I40E_MAX_BUFFER_TXD))

		return false;

		return false;





	if (skb_is_gso(skb))

		return __i40e_chk_linearize(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_ */
 
#endif /* _I40E_TXRX_H_ */

drivers/net/ethernet/intel/i40evf/i40e_txrx.c

+24 −25
Original line number Original line Diff line number Diff line
@@ -1796,35 +1796,34 @@ 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

 * @skb:      send buffer

 *

 *

 * Note: Our HW can't scatter-gather more than 8 fragments to build

 * Note: Our HW can't DMA more than 8 buffers to build a packet on the wire

 * a packet on the wire and so we need to figure out the cases where we

 * and so we need to figure out the cases where we need to linearize the skb.

 * 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)

bool __i40evf_chk_linearize(struct sk_buff *skb)

{

{

	const struct skb_frag_struct *frag, *stale;

	const struct skb_frag_struct *frag, *stale;

	int gso_size, nr_frags, sum;

	int 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;





	/* 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;

	nr_frags = skb_shinfo(skb)->nr_frags;

	if (nr_frags < I40E_MAX_BUFFER_TXD)

	if (nr_frags < (I40E_MAX_BUFFER_TXD - 1))

		return false;

		return false;





	/* We need to walk through the list and validate that each group

	/* 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

	 * 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

	 * to perform such validation on the last 6 since the last 6 cannot

	 * 6 cannot inherit any data from a descriptor before them, and the

	 * inherit any data from a descriptor after them.

	 * 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];

	frag = &skb_shinfo(skb)->frags[0];





	/* Initialize size to the negative value of gso_size minus 1.  We

	/* Initialize size to the negative value of gso_size minus 1.  We
@@ -1833,21 +1832,21 @@ bool __i40evf_chk_linearize(struct sk_buff *skb) 
	 * descriptors for a single transmit as the header and previous

	 * descriptors for a single transmit as the header and previous

	 * fragment are already consuming 2 descriptors.

	 * 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 */

	/* 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);

	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

	/* Walk through fragments adding latest fragment, testing it, and

	 * then removing stale fragments from the sum.

	 * then removing stale fragments from the sum.

	 */

	 */

	stale = &skb_shinfo(skb)->frags[0];

	stale = &skb_shinfo(skb)->frags[0];

	for (;;) {

	for (;;) {

		sum += skb_frag_size(++frag);

		sum += skb_frag_size(frag++);





		/* if sum is negative we failed to make sufficient progress */

		/* if sum is negative we failed to make sufficient progress */

		if (sum < 0)

		if (sum < 0)
@@ -1857,7 +1856,7 @@ bool __i40evf_chk_linearize(struct sk_buff *skb) 
		if (!--nr_frags)

		if (!--nr_frags)

			break;

			break;





		sum -= skb_frag_size(++stale);

		sum -= skb_frag_size(stale++);

	}

	}





	return false;

	return false;

drivers/net/ethernet/intel/i40evf/i40e_txrx.h

+7 −3
Original line number Original line Diff line number Diff line
@@ -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)

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 */

	/* Both TSO and single send will work if count is less than 8 */

	if (likely(count <= I40E_MAX_BUFFER_TXD))

	if (likely(count < I40E_MAX_BUFFER_TXD))

		return false;

		return false;





	if (skb_is_gso(skb))

		return __i40evf_chk_linearize(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_ */
 
#endif /* _I40E_TXRX_H_ */