From: Bailey Forrest bcf@google.com

The NIC requires each TSO segment to not span more than 10 descriptors. NIC further requires each descriptor to not exceed 16KB - 1 (GVE_TX_MAX_BUF_SIZE_DQO).

The descriptors for an skb are generated by gve_tx_add_skb_no_copy_dqo() for DQO RDA queue format. gve_tx_add_skb_no_copy_dqo() loops through each skb frag and generates a descriptor for the entire frag if the frag size is not greater than GVE_TX_MAX_BUF_SIZE_DQO. If the frag size is greater than GVE_TX_MAX_BUF_SIZE_DQO, it is split into descriptor(s) of size GVE_TX_MAX_BUF_SIZE_DQO and a descriptor is generated for the remainder (frag size % GVE_TX_MAX_BUF_SIZE_DQO).

gve_can_send_tso() checks if the descriptors thus generated for an skb would meet the requirement that each TSO-segment not span more than 10 descriptors. However, the current code misses an edge case when a TSO segment spans multiple descriptors within a large frag. This change fixes the edge case.

gve_can_send_tso() relies on the assumption that max gso size (9728) is less than GVE_TX_MAX_BUF_SIZE_DQO and therefore within an skb fragment a TSO segment can never span more than 2 descriptors.

Fixes: a57e5de476be ("gve: DQO: Add TX path") Signed-off-by: Praveen Kaligineedi pkaligineedi@google.com Signed-off-by: Bailey Forrest bcf@google.com Reviewed-by: Jeroen de Borst jeroendb@google.com Cc: stable@vger.kernel.org --- Changes from v1: - Added 'stable tag' - Added more explanation in the commit message - Modified comments to clarify the changes made - Changed variable names 'last_frag_size' to 'prev_frag_size' and 'last_frag_remain' to 'prev_frag_remain' - Removed parentheses around single line statement

drivers/net/ethernet/google/gve/gve_tx_dqo.c | 22 +++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/google/gve/gve_tx_dqo.c b/drivers/net/ethernet/google/gve/gve_tx_dqo.c index 0b3cca3fc792..f879426cb552 100644 --- a/drivers/net/ethernet/google/gve/gve_tx_dqo.c +++ b/drivers/net/ethernet/google/gve/gve_tx_dqo.c @@ -866,22 +866,42 @@ static bool gve_can_send_tso(const struct sk_buff *skb) const int header_len = skb_tcp_all_headers(skb); const int gso_size = shinfo->gso_size; int cur_seg_num_bufs; + int prev_frag_size; int cur_seg_size; int i;

cur_seg_size = skb_headlen(skb) - header_len; + prev_frag_size = skb_headlen(skb); cur_seg_num_bufs = cur_seg_size > 0;

for (i = 0; i < shinfo->nr_frags; i++) { if (cur_seg_size >= gso_size) { cur_seg_size %= gso_size; cur_seg_num_bufs = cur_seg_size > 0; + + if (prev_frag_size > GVE_TX_MAX_BUF_SIZE_DQO) { + int prev_frag_remain = prev_frag_size % + GVE_TX_MAX_BUF_SIZE_DQO; + + /* If the last descriptor of the previous frag + * is less than cur_seg_size, the segment will + * span two descriptors in the previous frag. + * Since max gso size (9728) is less than + * GVE_TX_MAX_BUF_SIZE_DQO, it is impossible + * for the segment to span more than two + * descriptors. + */ + if (prev_frag_remain && + cur_seg_size > prev_frag_remain) + cur_seg_num_bufs++; + } }

if (unlikely(++cur_seg_num_bufs > max_bufs_per_seg)) return false;

- cur_seg_size += skb_frag_size(&shinfo->frags[i]); + prev_frag_size = skb_frag_size(&shinfo->frags[i]); + cur_seg_size += prev_frag_size; }

return true;