Re: [PATCH v3 0/2] swiotlb: allocate padding slots if necessary

[Will Deacon]

Hi Petr,

On Thu, Mar 21, 2024 at 06:19:00PM +0100, Petr Tesarik wrote:
> From: Petr Tesarik <petr.tesarik1@xxxxxxxxxxxxxxxxxxx>
> 
> If the allocation alignment is bigger than IO_TLB_SIZE and min_align_mask
> covers some bits in the original address between IO_TLB_SIZE and
> alloc_align_mask, preserve these bits by allocating additional padding
> slots before the actual swiotlb buffer.

Thanks for fixing this! I was out at a conference last week, so I didn't
get very far with it myself, but I ended up in a pickle trying to avoid
extending 'struct io_tlb_slot'. Your solution is much better than the
crazy avenue I started going down...

With your changes, can we now simplify swiotlb_align_offset() to ignore
dma_get_min_align_mask() altogether and just:

	return addr & (IO_TLB_SIZE - 1);

?

Will