Re: [PATCH] arm64: swiotlb: Keep the default size for protected guests

On 07.08.2026 20:20, Jason Gunthorpe wrote:
> On Fri, Aug 07, 2026 at 06:13:49PM +0000, Mostafa Saleh wrote:
>> But the whole thing is best effort anyway, the kernel picks
>> IO_TLB_DEFAULT_SIZE which does not depend on the system topology or
>> how many devices or how much DMA they do.
>> SWIOTLB memory is wasted if unused so we should be careful around
>> that as it would be the other way around and users would have to
>> decrease it manually.
> Yeah, it is why the arch code shouldn't really be sizing it directly,
> it should be done in common code and, yes, we are probably going to
> have to do something alot smarter to have the common code better
> auto-tune this for the CC case..

What about the $subject patch? I assume that it is still needed to

restore the behavior that was altered by the "[PATCH v8 00/23]

dma-mapping: Track shared DMA state through direct, pool and swiotlb

paths?" patchset?

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland