mlx4_core: For 64-bit systems, vmap() kernel queue buffers

Since kernel virtual memory is not a problem on 64-bit systems, there
is no reason to use our own 2-layer page mapping scheme for large
kernel queue buffers on such systems.  Instead, map the page list to a
single virtually contiguous buffer with vmap(), so that can we access
buffer memory via direct indexing.

Signed-off-by: Michael S. Tsirkin <mst@dev.mellanox.co.il>
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

2 files changed, 18 insertions, 2 deletions

diff --git a/drivers/net/mlx4/alloc.c b/drivers/net/mlx4/alloc.c
index b226e019bc8b..2da2c2ec1f22 100644
--- a/drivers/net/mlx4/alloc.c
+++ b/drivers/net/mlx4/alloc.c
@@ -151,6 +151,19 @@ int mlx4_buf_alloc(struct mlx4_dev *dev, int size, int max_direct,
 
                         memset(buf->u.page_list[i].buf, 0, PAGE_SIZE);
                 }
+
+                if (BITS_PER_LONG == 64) {
+                        struct page **pages;
+                        pages = kmalloc(sizeof *pages * buf->nbufs, GFP_KERNEL);
+                        if (!pages)
+                                goto err_free;
+                        for (i = 0; i < buf->nbufs; ++i)
+                                pages[i] = virt_to_page(buf->u.page_list[i].buf);
+                        buf->u.direct.buf = vmap(pages, buf->nbufs, VM_MAP, PAGE_KERNEL);
+                        kfree(pages);
+                        if (!buf->u.direct.buf)
+                                goto err_free;
+                }
         }
 
         return 0;
@@ -170,6 +183,9 @@ void mlx4_buf_free(struct mlx4_dev *dev, int size, struct mlx4_buf *buf)
                 dma_free_coherent(&dev->pdev->dev, size, buf->u.direct.buf,
                                   buf->u.direct.map);
         else {
+                if (BITS_PER_LONG == 64)
+                        vunmap(buf->u.direct.buf);
+
                 for (i = 0; i < buf->nbufs; ++i)
                         if (buf->u.page_list[i].buf)
                                 dma_free_coherent(&dev->pdev->dev, PAGE_SIZE,
diff --git a/include/linux/mlx4/device.h b/include/linux/mlx4/device.h
index a0afa7511a30..631607788f83 100644
--- a/include/linux/mlx4/device.h
+++ b/include/linux/mlx4/device.h
@@ -189,7 +189,7 @@ struct mlx4_buf_list {
 };
 
 struct mlx4_buf {
-        union {
+        struct {
                 struct mlx4_buf_list    direct;
                 struct mlx4_buf_list   *page_list;
         } u;
@@ -310,7 +310,7 @@ int mlx4_buf_alloc(struct mlx4_dev *dev, int size, int max_direct,
 void mlx4_buf_free(struct mlx4_dev *dev, int size, struct mlx4_buf *buf);
 static inline void *mlx4_buf_offset(struct mlx4_buf *buf, int offset)
 {
-        if (buf->nbufs == 1)
+        if (BITS_PER_LONG == 64 || buf->nbufs == 1)
                 return buf->u.direct.buf + offset;
         else
                 return buf->u.page_list[offset >> PAGE_SHIFT].buf +