# Re: \[PATCH v6 20/20\] swiotlb: remove unused SWIOTLB\_FORCE flag

- From: Petr Tesarik \<hidden\>
- Date: 2026-06-09 13:44:52 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2026/06/17109498
- Thread: https://ratatoskr.run/linux-iommu/2026/06/17087574/t.md

```text
On Thu,  4 Jun 2026 14:09:59 +0530
"Aneesh Kumar K.V (Arm)" [ref] wrote:

> SWIOTLB_FORCE has no remaining in-tree users. Forced bouncing is now
> controlled through the swiotlb=force command line option via
> swiotlb_force_bounce.
> 
> Remove the unused flag and simplify the force_bounce initialization.
> 
> Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
> ---
>  include/linux/swiotlb.h | 1 -
>  kernel/dma/swiotlb.c    | 3 +--
>  2 files changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
> index 526f82e9da45..af88ca7182f4 100644
> --- a/include/linux/swiotlb.h
> +++ b/include/linux/swiotlb.h
> @@ -15,7 +15,6 @@ struct page;
>  struct scatterlist;
>  
>  #define SWIOTLB_VERBOSE	(1 << 0) /* verbose initialization */
> -#define SWIOTLB_FORCE	(1 << 1) /* force bounce buffering */
>  #define SWIOTLB_ANY	(1 << 2) /* allow any memory for the buffer */

These constants are kernel-internal, so let's not leave a hole in the
bitmask... I mean, what about changing SWIOTLB_ANY to (1 << 1) after
you remove SWIOTLB_FORCE?

Other than that, LGTM.

I consider this whole series a big step towards saner handling of
encrypted/decrypted memory for DMA buffers. Thank you for your effort!

Petr T

>  
>  /*
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index e4bd8c9eaeda..81cc4928e949 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -400,8 +400,7 @@ void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags,
>  	if (swiotlb_force_disable)
>  		return;
>  
> -	io_tlb_default_mem.force_bounce =
> -		swiotlb_force_bounce || (flags & SWIOTLB_FORCE);
> +	io_tlb_default_mem.force_bounce = swiotlb_force_bounce;
>  
>  #ifdef CONFIG_SWIOTLB_DYNAMIC
>  	if (!remap)


```