From 847a1d6796c767f8b697ead60997b847a84b897b Mon Sep 17 00:00:00 2001 From: Alexander Duyck Date: Wed, 2 Mar 2016 16:16:01 -0500 Subject: e1000: Do not overestimate descriptor counts in Tx pre-check The current code path is capable of grossly overestimating the number of descriptors needed to transmit a new frame. This specifically occurs if the skb contains a number of 4K pages. The issue is that the logic for determining the descriptors needed is ((S) >> (X)) + 1. When X is 12 it means that we were indicating that we required 2 descriptors for each 4K page when we only needed one. This change corrects this by instead adding (1 << (X)) - 1 to the S value instead of adding 1 after the fact. This way we get an accurate descriptor needed count as we are essentially doing a DIV_ROUNDUP(). Reported-by: Ivan Suzdal Signed-off-by: Alexander Duyck Tested-by: Aaron Brown Signed-off-by: Jeff Kirsher --- drivers/net/ethernet/intel/e1000/e1000_main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/net/ethernet/intel/e1000/e1000_main.c') diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c index 3fc7bde699ba..d213fb45855d 100644 --- a/drivers/net/ethernet/intel/e1000/e1000_main.c +++ b/drivers/net/ethernet/intel/e1000/e1000_main.c @@ -3106,7 +3106,7 @@ static int e1000_maybe_stop_tx(struct net_device *netdev, return __e1000_maybe_stop_tx(netdev, size); } -#define TXD_USE_COUNT(S, X) (((S) >> (X)) + 1) +#define TXD_USE_COUNT(S, X) (((S) + ((1 << (X)) - 1)) >> (X)) static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev) { -- cgit v1.2.3-59-g8ed1b From a4605fef7132f19afded76ee025c957558271a7d Mon Sep 17 00:00:00 2001 From: Alexander Duyck Date: Wed, 2 Mar 2016 16:16:08 -0500 Subject: e1000: Double Tx descriptors needed check for 82544 The 82544 has code that adds one additional descriptor per data buffer. However we weren't taking that into account when determining the descriptors needed for the next transmit at the end of the xmit_frame path. This change takes that into account by doubling the number of descriptors needed for the 82544 so that we can avoid a potential issue where we could hang the Tx ring by loading frames with xmit_more enabled and then stopping the ring without writing the tail. In addition it adds a few more descriptors to account for some additional workarounds that have been added over time. Signed-off-by: Alexander Duyck Tested-by: Aaron Brown Signed-off-by: Jeff Kirsher --- drivers/net/ethernet/intel/e1000/e1000_main.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) (limited to 'drivers/net/ethernet/intel/e1000/e1000_main.c') diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c index d213fb45855d..ae90d4f12b70 100644 --- a/drivers/net/ethernet/intel/e1000/e1000_main.c +++ b/drivers/net/ethernet/intel/e1000/e1000_main.c @@ -3256,12 +3256,29 @@ static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb, nr_frags, mss); if (count) { + /* The descriptors needed is higher than other Intel drivers + * due to a number of workarounds. The breakdown is below: + * Data descriptors: MAX_SKB_FRAGS + 1 + * Context Descriptor: 1 + * Keep head from touching tail: 2 + * Workarounds: 3 + */ + int desc_needed = MAX_SKB_FRAGS + 7; + netdev_sent_queue(netdev, skb->len); skb_tx_timestamp(skb); e1000_tx_queue(adapter, tx_ring, tx_flags, count); + + /* 82544 potentially requires twice as many data descriptors + * in order to guarantee buffers don't end on evenly-aligned + * dwords + */ + if (adapter->pcix_82544) + desc_needed += MAX_SKB_FRAGS + 1; + /* Make sure there is space in the ring for the next send. */ - e1000_maybe_stop_tx(netdev, tx_ring, MAX_SKB_FRAGS + 2); + e1000_maybe_stop_tx(netdev, tx_ring, desc_needed); if (!skb->xmit_more || netif_xmit_stopped(netdev_get_tx_queue(netdev, 0))) { -- cgit v1.2.3-59-g8ed1b