Patch "net: lan966x: Fix unmapping of received frames using FDMA" has been added to the 6.0-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    net: lan966x: Fix unmapping of received frames using FDMA

to the 6.0-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-lan966x-fix-unmapping-of-received-frames-using-f.patch
and it can be found in the queue-6.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 56aca823041ec4ca097620b521ae0ade4e8f4f5d
Author: Horatiu Vultur <horatiu.vultur@xxxxxxxxxxxxx>
Date:   Mon Oct 31 14:34:21 2022 +0100

    net: lan966x: Fix unmapping of received frames using FDMA
    
    [ Upstream commit fc57062f98b0b0ae52bc584d8fd5ac77c50df607 ]
    
    When lan966x was receiving a frame, then it was building the skb and
    after that it was calling dma_unmap_single with frame size as the
    length. This actually has 2 issues:
    1. It is using a length to map and a different length to unmap.
    2. When the unmap was happening, the data was sync for cpu but it could
       be that this will overwrite what build_skb was initializing.
    
    The fix for these two problems is to change the order of operations.
    First to sync the frame for cpu, then to build the skb and in the end to
    unmap using the correct size but without sync the frame again for cpu.
    
    Fixes: c8349639324a ("net: lan966x: Add FDMA functionality")
    Signed-off-by: Horatiu Vultur <horatiu.vultur@xxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20221031133421.1283196-1-horatiu.vultur@xxxxxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
index 407a6c125515..3a1a0f9178c0 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
@@ -414,13 +414,15 @@ static struct sk_buff *lan966x_fdma_rx_get_frame(struct lan966x_rx *rx)
 	/* Get the received frame and unmap it */
 	db = &rx->dcbs[rx->dcb_index].db[rx->db_index];
 	page = rx->page[rx->dcb_index][rx->db_index];
+
+	dma_sync_single_for_cpu(lan966x->dev, (dma_addr_t)db->dataptr,
+				FDMA_DCB_STATUS_BLOCKL(db->status),
+				DMA_FROM_DEVICE);
+
 	skb = build_skb(page_address(page), PAGE_SIZE << rx->page_order);
 	if (unlikely(!skb))
 		goto unmap_page;
 
-	dma_unmap_single(lan966x->dev, (dma_addr_t)db->dataptr,
-			 FDMA_DCB_STATUS_BLOCKL(db->status),
-			 DMA_FROM_DEVICE);
 	skb_put(skb, FDMA_DCB_STATUS_BLOCKL(db->status));
 
 	lan966x_ifh_get_src_port(skb->data, &src_port);
@@ -429,6 +431,10 @@ static struct sk_buff *lan966x_fdma_rx_get_frame(struct lan966x_rx *rx)
 	if (WARN_ON(src_port >= lan966x->num_phys_ports))
 		goto free_skb;
 
+	dma_unmap_single_attrs(lan966x->dev, (dma_addr_t)db->dataptr,
+			       PAGE_SIZE << rx->page_order, DMA_FROM_DEVICE,
+			       DMA_ATTR_SKIP_CPU_SYNC);
+
 	skb->dev = lan966x->ports[src_port]->dev;
 	skb_pull(skb, IFH_LEN * sizeof(u32));
 
@@ -454,9 +460,9 @@ static struct sk_buff *lan966x_fdma_rx_get_frame(struct lan966x_rx *rx)
 free_skb:
 	kfree_skb(skb);
 unmap_page:
-	dma_unmap_page(lan966x->dev, (dma_addr_t)db->dataptr,
-		       FDMA_DCB_STATUS_BLOCKL(db->status),
-		       DMA_FROM_DEVICE);
+	dma_unmap_single_attrs(lan966x->dev, (dma_addr_t)db->dataptr,
+			       PAGE_SIZE << rx->page_order, DMA_FROM_DEVICE,
+			       DMA_ATTR_SKIP_CPU_SYNC);
 	__free_pages(page, rx->page_order);
 
 	return NULL;