net: mvpp2: fix dma unmapping of TX buffers for fragments

Since commit 71ce391dfb784 ("net: mvpp2: enable proper per-CPU TX
buffers unmapping"), we are not correctly DMA unmapping TX buffers for
fragments.

Indeed, the mvpp2_txq_inc_put() function only stores in the
txq_cpu->tx_buffs[] array the physical address of the buffer to be
DMA-unmapped when skb != NULL. In addition, when DMA-unmapping, we use
skb_headlen(skb) to get the size to be unmapped. Both of this works fine
for TX descriptors that are associated directly to a SKB, but not the
ones that are used for fragments, with a NULL pointer as skb:

 - We have a NULL physical address when calling DMA unmap
 - skb_headlen(skb) crashes because skb is NULL

This causes random crashes when fragments are used.

To solve this problem, we need to:

 - Store the physical address of the buffer to be unmapped
   unconditionally, regardless of whether it is tied to a SKB or not.

 - Store the length of the buffer to be unmapped, which requires a new
   field.

Instead of adding a third array to store the length of the buffer to be
unmapped, and as suggested by David Miller, this commit refactors the
tx_buffs[] and tx_skb[] arrays of 'struct mvpp2_txq_pcpu' into a
separate structure 'mvpp2_txq_pcpu_buf', to which a 'size' field is
added. Therefore, instead of having three arrays to allocate/free, we
have a single one, which also improve data locality, reducing the
impact on the CPU cache.

Fixes: 71ce391dfb784 ("net: mvpp2: enable proper per-CPU TX buffers unmapping")
Reported-by: Raphael G <raphael.glon@corp.ovh.com>
Cc: Raphael G <raphael.glon@corp.ovh.com>
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/marvell/mvpp2.c b/drivers/net/ethernet/marvell/mvpp2.c
index dabc5418efcc48287b1e30d95f8a05235755f119..cda04b3126bc688222eaebed0fbe5c59aa76f89b 100644 (file)
--- a/drivers/net/ethernet/marvell/mvpp2.c
+++ b/drivers/net/ethernet/marvell/mvpp2.c
@@ -770,6 +770,17 @@ struct mvpp2_rx_desc {
        u32 reserved8;
 };
 
+struct mvpp2_txq_pcpu_buf {
+       /* Transmitted SKB */
+       struct sk_buff *skb;
+
+       /* Physical address of transmitted buffer */
+       dma_addr_t phys;
+
+       /* Size transmitted */
+       size_t size;
+};
+
 /* Per-CPU Tx queue control */
 struct mvpp2_txq_pcpu {
        int cpu;
@@ -785,11 +796,8 @@ struct mvpp2_txq_pcpu {
        /* Number of Tx DMA descriptors reserved for each CPU */
        int reserved_num;
 
-       /* Array of transmitted skb */
-       struct sk_buff **tx_skb;
-
-       /* Array of transmitted buffers' physical addresses */
-       dma_addr_t *tx_buffs;
+       /* Infos about transmitted buffers */
+       struct mvpp2_txq_pcpu_buf *buffs;
 
        /* Index of last TX DMA descriptor that was inserted */
        int txq_put_index;
@@ -979,10 +987,11 @@ static void mvpp2_txq_inc_put(struct mvpp2_txq_pcpu *txq_pcpu,
                              struct sk_buff *skb,
                              struct mvpp2_tx_desc *tx_desc)
 {
-       txq_pcpu->tx_skb[txq_pcpu->txq_put_index] = skb;
-       if (skb)
-               txq_pcpu->tx_buffs[txq_pcpu->txq_put_index] =
-                                                        tx_desc->buf_phys_addr;
+       struct mvpp2_txq_pcpu_buf *tx_buf =
+               txq_pcpu->buffs + txq_pcpu->txq_put_index;
+       tx_buf->skb = skb;
+       tx_buf->size = tx_desc->data_size;
+       tx_buf->phys = tx_desc->buf_phys_addr;
        txq_pcpu->txq_put_index++;
        if (txq_pcpu->txq_put_index == txq_pcpu->size)
                txq_pcpu->txq_put_index = 0;
@@ -4401,17 +4410,16 @@ static void mvpp2_txq_bufs_free(struct mvpp2_port *port,
        int i;
 
        for (i = 0; i < num; i++) {
-               dma_addr_t buf_phys_addr =
-                                   txq_pcpu->tx_buffs[txq_pcpu->txq_get_index];
-               struct sk_buff *skb = txq_pcpu->tx_skb[txq_pcpu->txq_get_index];
+               struct mvpp2_txq_pcpu_buf *tx_buf =
+                       txq_pcpu->buffs + txq_pcpu->txq_get_index;
 
                mvpp2_txq_inc_get(txq_pcpu);
 
-               dma_unmap_single(port->dev->dev.parent, buf_phys_addr,
-                                skb_headlen(skb), DMA_TO_DEVICE);
-               if (!skb)
+               dma_unmap_single(port->dev->dev.parent, tx_buf->phys,
+                                tx_buf->size, DMA_TO_DEVICE);
+               if (!tx_buf->skb)
                        continue;
-               dev_kfree_skb_any(skb);
+               dev_kfree_skb_any(tx_buf->skb);
        }
 }
 
@@ -4651,15 +4659,10 @@ static int mvpp2_txq_init(struct mvpp2_port *port,
        for_each_present_cpu(cpu) {
                txq_pcpu = per_cpu_ptr(txq->pcpu, cpu);
                txq_pcpu->size = txq->size;
-               txq_pcpu->tx_skb = kmalloc(txq_pcpu->size *
-                                          sizeof(*txq_pcpu->tx_skb),
-                                          GFP_KERNEL);
-               if (!txq_pcpu->tx_skb)
-                       goto error;
-
-               txq_pcpu->tx_buffs = kmalloc(txq_pcpu->size *
-                                            sizeof(dma_addr_t), GFP_KERNEL);
-               if (!txq_pcpu->tx_buffs)
+               txq_pcpu->buffs = kmalloc(txq_pcpu->size *
+                                         sizeof(struct mvpp2_txq_pcpu_buf),
+                                         GFP_KERNEL);
+               if (!txq_pcpu->buffs)
                        goto error;
 
                txq_pcpu->count = 0;
@@ -4673,8 +4676,7 @@ static int mvpp2_txq_init(struct mvpp2_port *port,
 error:
        for_each_present_cpu(cpu) {
                txq_pcpu = per_cpu_ptr(txq->pcpu, cpu);
-               kfree(txq_pcpu->tx_skb);
-               kfree(txq_pcpu->tx_buffs);
+               kfree(txq_pcpu->buffs);
        }
 
        dma_free_coherent(port->dev->dev.parent,
@@ -4693,8 +4695,7 @@ static void mvpp2_txq_deinit(struct mvpp2_port *port,
 
        for_each_present_cpu(cpu) {
                txq_pcpu = per_cpu_ptr(txq->pcpu, cpu);
-               kfree(txq_pcpu->tx_skb);
-               kfree(txq_pcpu->tx_buffs);
+               kfree(txq_pcpu->buffs);
        }
 
        if (txq->descs)