[Xenial][Artful][PATCH 2/2] i40e/i40evf: Account for frags split over multiple descriptors in check linearize
Dan Streetman
ddstreet at canonical.com
Wed Mar 21 12:36:54 UTC 2018
sorry for the duplicates, i thought it was a mail server issue on my
end at first but looks like they all finally made it thru.
On Tue, Mar 20, 2018 at 11:40 AM, Dan Streetman <ddstreet at canonical.com> wrote:
> From: Alexander Duyck <alexander.h.duyck at intel.com>
>
> BugLink: http://bugs.launchpad.net/bugs/1723127
>
> The original code for __i40e_chk_linearize didn't take into account the
> fact that if a fragment is 16K in size or larger it has to be split over 2
> descriptors and the smaller of those 2 descriptors will be on the trailing
> edge of the transmit. As a result we can get into situations where we didn't
> catch requests that could result in a Tx hang.
>
> This patch takes care of that by subtracting the length of all but the
> trailing edge of the stale fragment before we test for sum. By doing this
> we can guarantee that we have all cases covered, including the case of a
> fragment that spans multiple descriptors. We don't need to worry about
> checking the inner portions of this since 12K is the maximum aligned DMA
> size and that is larger than any MSS will ever be since the MTU limit for
> jumbos is something on the order of 9K.
>
> Signed-off-by: Alexander Duyck <alexander.h.duyck at intel.com>
> Tested-by: Andrew Bowers <andrewx.bowers at intel.com>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher at intel.com>
> (cherry-picked from 248de22e638f10bd5bfc7624a357f940f66ba137)
> Signed-off-by: Dan Streetman <ddstreet at canonical.com>
>
> ---
> Note that this patch applies to Xenial and Artful, but the previous patch
> in the series is only required in Xenial.
>
> drivers/net/ethernet/intel/i40e/i40e_txrx.c | 26 +++++++++++++++++++++++---
> drivers/net/ethernet/intel/i40evf/i40e_txrx.c | 26 +++++++++++++++++++++++---
> 2 files changed, 46 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> index a18c91e33dea..2c83a6ce1b47 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> @@ -2640,10 +2640,30 @@ bool __i40e_chk_linearize(struct sk_buff *skb)
> /* Walk through fragments adding latest fragment, testing it, and
> * then removing stale fragments from the sum.
> */
> - stale = &skb_shinfo(skb)->frags[0];
> - for (;;) {
> + for (stale = &skb_shinfo(skb)->frags[0];; stale++) {
> + int stale_size = skb_frag_size(stale);
> +
> sum += skb_frag_size(frag++);
>
> + /* The stale fragment may present us with a smaller
> + * descriptor than the actual fragment size. To account
> + * for that we need to remove all the data on the front and
> + * figure out what the remainder would be in the last
> + * descriptor associated with the fragment.
> + */
> + if (stale_size > I40E_MAX_DATA_PER_TXD) {
> + int align_pad = -(stale->page_offset) &
> + (I40E_MAX_READ_REQ_SIZE - 1);
> +
> + sum -= align_pad;
> + stale_size -= align_pad;
> +
> + do {
> + sum -= I40E_MAX_DATA_PER_TXD_ALIGNED;
> + stale_size -= I40E_MAX_DATA_PER_TXD_ALIGNED;
> + } while (stale_size > I40E_MAX_DATA_PER_TXD);
> + }
> +
> /* if sum is negative we failed to make sufficient progress */
> if (sum < 0)
> return true;
> @@ -2651,7 +2671,7 @@ bool __i40e_chk_linearize(struct sk_buff *skb)
> if (!nr_frags--)
> break;
>
> - sum -= skb_frag_size(stale++);
> + sum -= stale_size;
> }
>
> return false;
> diff --git a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
> index f2163735528d..1f48bcdf1ea5 100644
> --- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
> +++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
> @@ -1843,10 +1843,30 @@ bool __i40evf_chk_linearize(struct sk_buff *skb)
> /* Walk through fragments adding latest fragment, testing it, and
> * then removing stale fragments from the sum.
> */
> - stale = &skb_shinfo(skb)->frags[0];
> - for (;;) {
> + for (stale = &skb_shinfo(skb)->frags[0];; stale++) {
> + int stale_size = skb_frag_size(stale);
> +
> sum += skb_frag_size(frag++);
>
> + /* The stale fragment may present us with a smaller
> + * descriptor than the actual fragment size. To account
> + * for that we need to remove all the data on the front and
> + * figure out what the remainder would be in the last
> + * descriptor associated with the fragment.
> + */
> + if (stale_size > I40E_MAX_DATA_PER_TXD) {
> + int align_pad = -(stale->page_offset) &
> + (I40E_MAX_READ_REQ_SIZE - 1);
> +
> + sum -= align_pad;
> + stale_size -= align_pad;
> +
> + do {
> + sum -= I40E_MAX_DATA_PER_TXD_ALIGNED;
> + stale_size -= I40E_MAX_DATA_PER_TXD_ALIGNED;
> + } while (stale_size > I40E_MAX_DATA_PER_TXD);
> + }
> +
> /* if sum is negative we failed to make sufficient progress */
> if (sum < 0)
> return true;
> @@ -1854,7 +1874,7 @@ bool __i40evf_chk_linearize(struct sk_buff *skb)
> if (!nr_frags--)
> break;
>
> - sum -= skb_frag_size(stale++);
> + sum -= stale_size;
> }
>
> return false;
> --
> 2.15.1
>
>
> --
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