[PATCH bpf-next] xsk: Simplify xp_aligned_validate_desc implementation

[PATCH bpf-next] xsk: Simplify xp_aligned_validate_desc implementation

[Kal Conley]

Perform the chunk boundary check like the page boundary check in
xp_desc_crosses_non_contig_pg(). This simplifies the implementation and
reduces the number of branches.

Signed-off-by: Kal Conley <kal.conley@dectris.com>
---
 net/xdp/xsk_queue.h | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
index dea4f378327d..6d40a77fccbe 100644
--- a/net/xdp/xsk_queue.h
+++ b/net/xdp/xsk_queue.h
@@ -133,16 +133,12 @@ static inline bool xskq_cons_read_addr_unchecked(struct xsk_queue *q, u64 *addr)
 static inline bool xp_aligned_validate_desc(struct xsk_buff_pool *pool,
 					    struct xdp_desc *desc)
 {
-	u64 chunk, chunk_end;
+	u64 offset = desc->addr & (pool->chunk_size - 1);
 
-	chunk = xp_aligned_extract_addr(pool, desc->addr);
-	if (likely(desc->len)) {
-		chunk_end = xp_aligned_extract_addr(pool, desc->addr + desc->len - 1);
-		if (chunk != chunk_end)
-			return false;
-	}
+	if (offset + desc->len > pool->chunk_size)
+		return false;
 
-	if (chunk >= pool->addrs_cnt)
+	if (desc->addr >= pool->addrs_cnt)
 		return false;
 
 	if (desc->options)
-- 
2.39.2

Re: [PATCH bpf-next] xsk: Simplify xp_aligned_validate_desc implementation

[Magnus Karlsson]

On Mon, 10 Apr 2023 at 14:24, Kal Conley <kal.conley@dectris.com> wrote:
>
> Perform the chunk boundary check like the page boundary check in
> xp_desc_crosses_non_contig_pg(). This simplifies the implementation and
> reduces the number of branches.

Thanks for this simplification Kal. Just to check, does your change
pass the xsk selftests, especially the INV_DESC test? If so, then you
have my ack below.

Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>

> Signed-off-by: Kal Conley <kal.conley@dectris.com>
> ---
>  net/xdp/xsk_queue.h | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
>
> diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
> index dea4f378327d..6d40a77fccbe 100644
> --- a/net/xdp/xsk_queue.h
> +++ b/net/xdp/xsk_queue.h
> @@ -133,16 +133,12 @@ static inline bool xskq_cons_read_addr_unchecked(struct xsk_queue *q, u64 *addr)
>  static inline bool xp_aligned_validate_desc(struct xsk_buff_pool *pool,
>                                             struct xdp_desc *desc)
>  {
> -       u64 chunk, chunk_end;
> +       u64 offset = desc->addr & (pool->chunk_size - 1);
>
> -       chunk = xp_aligned_extract_addr(pool, desc->addr);
> -       if (likely(desc->len)) {
> -               chunk_end = xp_aligned_extract_addr(pool, desc->addr + desc->len - 1);
> -               if (chunk != chunk_end)
> -                       return false;
> -       }
> +       if (offset + desc->len > pool->chunk_size)
> +               return false;
>
> -       if (chunk >= pool->addrs_cnt)
> +       if (desc->addr >= pool->addrs_cnt)
>                 return false;
>
>         if (desc->options)
> --
> 2.39.2
>

Re: [PATCH bpf-next] xsk: Simplify xp_aligned_validate_desc implementation

[Kal Cutter Conley]

> > Perform the chunk boundary check like the page boundary check in
> > xp_desc_crosses_non_contig_pg(). This simplifies the implementation and
> > reduces the number of branches.
>
> Thanks for this simplification Kal. Just to check, does your change
> pass the xsk selftests, especially the INV_DESC test? If so, then you
> have my ack below.
>
> Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>

Yes, I ran the XSK selftests and they all PASSED.

Re: [PATCH bpf-next] xsk: Simplify xp_aligned_validate_desc implementation

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <daniel@iogearbox.net>:

On Mon, 10 Apr 2023 14:18:41 +0200 you wrote:
> Perform the chunk boundary check like the page boundary check in
> xp_desc_crosses_non_contig_pg(). This simplifies the implementation and
> reduces the number of branches.
> 
> Signed-off-by: Kal Conley <kal.conley@dectris.com>
> ---
>  net/xdp/xsk_queue.h | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)

Here is the summary with links:
  - [bpf-next] xsk: Simplify xp_aligned_validate_desc implementation
    https://git.kernel.org/bpf/bpf-next/c/0c5f48599bed

You are awesome, thank you!
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