target/linux/layerscape/patches-5.4/701-net-0022-sdk_dpaa-ls1043a-errata-realign-and-linearize-egress.patch

   1 From 9821d27a36704d19c57d4b6c52585b9868703633 Mon Sep 17 00:00:00 2001
   2 From: Camelia Groza <camelia.groza@nxp.com>
   3 Date: Mon, 4 Sep 2017 13:41:17 +0300
   4 Subject: [PATCH] sdk_dpaa: ls1043a errata: realign and linearize egress skbs
   5
   6 Allocate a new page and copy the skb's contents to it in order to
   7 guarantee that 4k boundary crossings do not occur.
   8
   9 Signed-off-by: Camelia Groza <camelia.groza@nxp.com>
  10 ---
  11  .../net/ethernet/freescale/sdk_dpaa/dpaa_eth_sg.c  | 159 +++++++++++----------
  12  1 file changed, 84 insertions(+), 75 deletions(-)
  13
  14 --- a/drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_sg.c
  15 +++ b/drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_sg.c
  16 @@ -742,86 +742,94 @@ int __hot skb_to_contig_fd(struct dpa_pr
  17  EXPORT_SYMBOL(skb_to_contig_fd);
  18
  19  #ifndef CONFIG_PPC
  20 -struct sk_buff *split_skb_at_4k_boundaries(struct sk_buff *skb)
  21 +/* Verify the conditions that trigger the A010022 errata: 4K memory address
  22 + * crossings.
  23 + */
  24 +bool a010022_check_skb(struct sk_buff *skb)
  25  {
  26 -       unsigned int length, nr_frags, moved_len = 0;
  27 -       u64 page_start;
  28 -       struct page *page;
  29 +       int nr_frags, i = 0;
  30         skb_frag_t *frag;
  31 -       int i = 0, j = 0;
  32
  33 -       /* make sure skb is not shared */
  34 -       skb = skb_share_check(skb, GFP_ATOMIC);
  35 -       if (!skb)
  36 -               return NULL;
  37 +       /* Check if the headroom crosses a boundary */
  38 +       if (HAS_DMA_ISSUE(skb->head, skb_headroom(skb)))
  39 +               return true;
  40 +
  41 +       /* Check if the non-paged data crosses a boundary */
  42 +       if (HAS_DMA_ISSUE(skb->data, skb_headlen(skb)))
  43 +               return true;
  44 +
  45 +       /* Check if the entire linear skb crosses a boundary */
  46 +       if (HAS_DMA_ISSUE(skb->head, skb_end_offset(skb)))
  47 +               return true;
  48
  49         nr_frags = skb_shinfo(skb)->nr_frags;
  50 -       page_start = (u64)skb->data;
  51
  52 -       /* split the linear part at the first 4k boundary and create one (big)
  53 -        * fragment with the rest
  54 -        */
  55 -       if (HAS_DMA_ISSUE(skb->data, skb_headlen(skb))) {
  56 -               /* we'll add one more frag, make sure there's room */
  57 -               if (nr_frags + 1 > DPA_SGT_MAX_ENTRIES)
  58 -                       return NULL;
  59 -
  60 -               /* next page boundary */
  61 -               page_start = (page_start + 0x1000) & ~0xFFF;
  62 -               page = virt_to_page(page_start);
  63 -
  64 -               /* move the rest of fragments to make room for a new one at j */
  65 -               for (i = nr_frags - 1; i >= j;  i--)
  66 -                       skb_shinfo(skb)->frags[i + 1] = skb_shinfo(skb)->frags[i];
  67 -
  68 -               /* move length bytes to a paged fragment at j */
  69 -               length = min((u64)0x1000,
  70 -                            (u64)skb->data + skb_headlen(skb) - page_start);
  71 -               skb->data_len += length;
  72 -               moved_len += length;
  73 -               skb_fill_page_desc(skb, j++, page, 0, length);
  74 -               get_page(page);
  75 -               skb_shinfo(skb)->nr_frags = ++nr_frags;
  76 +       while (i < nr_frags) {
  77 +               frag = &skb_shinfo(skb)->frags[i];
  78 +
  79 +               /* Check if the paged fragment crosses a boundary from its
  80 +                * offset to its end.
  81 +                */
  82 +               if (HAS_DMA_ISSUE(frag->page_offset, frag->size))
  83 +                       return true;
  84 +
  85 +               i++;
  86         }
  87 -       /* adjust the tail pointer */
  88 -       skb->tail -= moved_len;
  89 -       j = 0;
  90 -
  91 -       /* split any paged fragment that crosses a 4K boundary */
  92 -       while (j < nr_frags) {
  93 -               frag = &skb_shinfo(skb)->frags[j];
  94 -
  95 -               /* if there is a 4K boundary between the fragment's offset and end */
  96 -               if (HAS_DMA_ISSUE(frag->page_offset, frag->size)) {
  97 -                       /* we'll add one more frag, make sure there's room */
  98 -                       if (nr_frags + 1 > DPA_SGT_MAX_ENTRIES)
  99 -                               return NULL;
 100 -
 101 -                       /* new page boundary */
 102 -                       page_start = (u64)page_address(skb_frag_page(frag)) +
 103 -                                                 frag->page_offset + 0x1000;
 104 -                       page_start = (u64)page_start & ~0xFFF;
 105 -                       page = virt_to_page(page_start);
 106 -
 107 -                       /* move the rest of fragments to make room for a new one at j+1 */
 108 -                       for (i = nr_frags - 1; i > j;  i--)
 109 -                               skb_shinfo(skb)->frags[i + 1] =
 110 -                                               skb_shinfo(skb)->frags[i];
 111 -
 112 -                       /* move length bytes to a new paged fragment at j+1 */
 113 -                       length = (u64)page_address(skb_frag_page(frag)) +
 114 -                                frag->page_offset + frag->size - page_start;
 115 -                       frag->size -= length;
 116 -                       skb_fill_page_desc(skb, j + 1, page, 0, length);
 117 -                       get_page(page);
 118 -                       skb_shinfo(skb)->nr_frags = ++nr_frags;
 119 -               }
 120
 121 -               /* move to next frag */
 122 -               j++;
 123 +       return false;
 124 +}
 125 +
 126 +/* Realign the skb by copying its contents at the start of a newly allocated
 127 + * page. Build a new skb around the new buffer and release the old one.
 128 + * A performance drop should be expected.
 129 + */
 130 +struct sk_buff *a010022_realign_skb(struct sk_buff *skb)
 131 +{
 132 +       int headroom = skb_headroom(skb);
 133 +       struct sk_buff *nskb = NULL;
 134 +       struct page *npage;
 135 +       void *npage_addr;
 136 +       int nsize;
 137 +
 138 +       npage = alloc_page(GFP_ATOMIC);
 139 +       if (unlikely(!npage)) {
 140 +               WARN_ONCE(1, "Memory allocation failure\n");
 141 +               return NULL;
 142 +       }
 143 +       npage_addr = page_address(npage);
 144 +
 145 +       /* For the new skb we only need the old one's data (both non-paged and
 146 +        * paged) and a headroom large enough to fit our private info. We can
 147 +        * skip the old tailroom.
 148 +        *
 149 +        * Make sure the new linearized buffer will not exceed a page's size.
 150 +        */
 151 +       nsize = headroom + skb->len +
 152 +               SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
 153 +       if (unlikely(nsize > 4096))
 154 +               goto err;
 155 +
 156 +       nskb = build_skb(npage_addr, nsize);
 157 +       if (unlikely(!nskb))
 158 +               goto err;
 159 +
 160 +       /* Code borrowed and adapted from skb_copy() */
 161 +       skb_reserve(nskb, headroom);
 162 +       skb_put(nskb, skb->len);
 163 +       if (skb_copy_bits(skb, 0, nskb->data, skb->len)) {
 164 +               WARN_ONCE(1, "skb parsing failure\n");
 165 +               goto err;
 166         }
 167 +       copy_skb_header(nskb, skb);
 168 +
 169 +       dev_kfree_skb(skb);
 170 +       return nskb;
 171
 172 -       return skb;
 173 +err:
 174 +       if (nskb)
 175 +               dev_kfree_skb(nskb);
 176 +       put_page(npage);
 177 +       return NULL;
 178  }
 179  #endif
 180
 181 @@ -1016,9 +1024,9 @@ int __hot dpa_tx_extended(struct sk_buff
 182  #endif /* CONFIG_FSL_DPAA_TS */
 183
 184  #ifndef CONFIG_PPC
 185 -resplit_4k:
 186 -       if (unlikely(dpaa_errata_a010022)) {
 187 -               skb = split_skb_at_4k_boundaries(skb);
 188 +realign_4k:
 189 +       if (unlikely(dpaa_errata_a010022) && a010022_check_skb(skb)) {
 190 +               skb = a010022_realign_skb(skb);
 191                 if (!skb)
 192                         goto skb_to_fd_failed;
 193         }
 194 @@ -1064,8 +1072,9 @@ resplit_4k:
 195                         kfree_skb(skb);
 196                         skb = nskb;
 197  #ifndef CONFIG_PPC
 198 -                       if (unlikely(dpaa_errata_a010022))
 199 -                               goto resplit_4k;
 200 +                       if (unlikely(dpaa_errata_a010022) &&
 201 +                           a010022_check_skb(skb))
 202 +                               goto realign_4k;
 203  #endif
 204                         /* skb_copy() has now linearized the skbuff. */
 205                 } else if (unlikely(nonlinear)) {