[PATCH] xsk: Fix offset calculation in unaligned mode

[PATCH] xsk: Fix offset calculation in unaligned mode

[e.kubanski]

Offset calculation in unaligned mode didn't
match previous behaviour.

Unaligned mode should pass offset only in
upper 16 bits, lower 48 bits should pass
only specific chunk location in umem.

pool->headroom was duplicated into offset
and address of the umem chunk.

Signed-off-by: Eryk Kubanski <e.kubanski@partner.samsung.com>
---
 include/net/xsk_buff_pool.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h
index 7f0a75d6563d..b3699a848844 100644
--- a/include/net/xsk_buff_pool.h
+++ b/include/net/xsk_buff_pool.h
@@ -232,8 +232,8 @@ static inline u64 xp_get_handle(struct xdp_buff_xsk *xskb,
 		return orig_addr;
 
 	offset = xskb->xdp.data - xskb->xdp.data_hard_start;
-	orig_addr -= offset;
 	offset += pool->headroom;
+	orig_addr -= offset;
 	return orig_addr + (offset << XSK_UNALIGNED_BUF_OFFSET_SHIFT);
 }
 
-- 
2.34.1

Re: [PATCH] xsk: Fix offset calculation in unaligned mode

[Maciej Fijalkowski]

On Wed, Apr 09, 2025 at 03:19:13PM +0200, e.kubanski wrote:
> Offset calculation in unaligned mode didn't
> match previous behaviour.
> 
> Unaligned mode should pass offset only in
> upper 16 bits, lower 48 bits should pass
> only specific chunk location in umem.
> 
> pool->headroom was duplicated into offset
> and address of the umem chunk.

Thanks! Same what Magnus commented, you need to target the patch to bpf
tree and provide a fixes tag. Here's the format that we expect:

Fixes: bea14124bacb ("xsk: Get rid of xdp_buff_xsk::orig_addr")

and it actually is the blamed commit for this fix, so just paste it to
commit message.

Also, we prefer to use imperative mood in commit descriptions. Go through
https://docs.kernel.org/process/submitting-patches.html.

> 
> Signed-off-by: Eryk Kubanski <e.kubanski@partner.samsung.com>
> ---
>  include/net/xsk_buff_pool.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h
> index 7f0a75d6563d..b3699a848844 100644
> --- a/include/net/xsk_buff_pool.h
> +++ b/include/net/xsk_buff_pool.h
> @@ -232,8 +232,8 @@ static inline u64 xp_get_handle(struct xdp_buff_xsk *xskb,
>  		return orig_addr;
>  
>  	offset = xskb->xdp.data - xskb->xdp.data_hard_start;
> -	orig_addr -= offset;
>  	offset += pool->headroom;
> +	orig_addr -= offset;
>  	return orig_addr + (offset << XSK_UNALIGNED_BUF_OFFSET_SHIFT);
>  }
>  
> -- 
> 2.34.1
>