[PATCH 3.16 182/306] net/mlx5: Avoid passing dma address 0 to firmware

[Ben Hutchings]

3.16.40-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Noa Osherovich <no...@mellanox.com>

commit 6b276190c50a12511d889d9079ffb901ff94a822 upstream.

Currently the firmware can't work with a page with dma address 0.
Passing such an address to the firmware will cause the give_pages
command to fail.

To avoid this, in case we get a 0 dma address of a page from the
dma engine, we avoid passing it to FW by remapping to get an address
other than 0.

Fixes: bf0bf77f6519 ('mlx5: Support communicating arbitrary host...')
Signed-off-by: Noa Osherovich <no...@mellanox.com>
Signed-off-by: Saeed Mahameed <sae...@mellanox.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
 .../net/ethernet/mellanox/mlx5/core/pagealloc.c    | 26 +++++++++++++++-------
 1 file changed, 18 insertions(+), 8 deletions(-)

--- a/drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c
@@ -243,6 +243,7 @@ static void free_4k(struct mlx5_core_dev
 static int alloc_system_page(struct mlx5_core_dev *dev, u16 func_id)
 {
        struct page *page;
+       u64 zero_addr = 1;
        u64 addr;
        int err;
 
@@ -251,26 +252,35 @@ static int alloc_system_page(struct mlx5
                mlx5_core_warn(dev, "failed to allocate page\n");
                return -ENOMEM;
        }
+map:
        addr = dma_map_page(&dev->pdev->dev, page, 0,
                            PAGE_SIZE, DMA_BIDIRECTIONAL);
        if (dma_mapping_error(&dev->pdev->dev, addr)) {
                mlx5_core_warn(dev, "failed dma mapping page\n");
                err = -ENOMEM;
-               goto out_alloc;
+               goto err_mapping;
        }
+
+       /* Firmware doesn't support page with physical address 0 */
+       if (addr == 0) {
+               zero_addr = addr;
+               goto map;
+       }
+
        err = insert_page(dev, addr, page, func_id);
        if (err) {
                mlx5_core_err(dev, "failed to track allocated page\n");
-               goto out_mapping;
+               dma_unmap_page(&dev->pdev->dev, addr, PAGE_SIZE,
+                              DMA_BIDIRECTIONAL);
        }
 
-       return 0;
-
-out_mapping:
-       dma_unmap_page(&dev->pdev->dev, addr, PAGE_SIZE, DMA_BIDIRECTIONAL);
+err_mapping:
+       if (err)
+               __free_page(page);
 
-out_alloc:
-       __free_page(page);
+       if (zero_addr == 0)
+               dma_unmap_page(&dev->pdev->dev, zero_addr, PAGE_SIZE,
+                              DMA_BIDIRECTIONAL);
 
        return err;
 }