swiotlb cleanups v3

[Tom Lendacky]

> Hi Konrad,
>
> this series contains a bunch of swiotlb cleanups, mostly to reduce the
> amount of internals exposed to code outside of swiotlb.c, which should
> helper to prepare for supporting multiple different bounce buffer pools.

Somewhere between the 1st and 2nd patch, specifying a specific swiotlb
for an SEV guest is no longer honored. For example, if I start an SEV
guest with 16GB of memory and specify swiotlb=131072 I used to get a
256MB SWIOTLB. However, after the 2nd patch, the swiotlb=131072 is no
longer honored and I get a 982MB SWIOTLB (as set via sev_setup_arch() in
arch/x86/mm/mem_encrypt.c).

I can't be sure which patch caused the issue since an SEV guest fails to
boot with the 1st patch but can boot with the 2nd patch, at which point
the SWIOTLB comes in at 982MB (I haven't had a chance to debug it and so
I'm hoping you might be able to quickly spot what's going on).

Thanks,
Tom

>
> Changes since v2:
>  - fix a bisetion hazard that did not allocate the alloc_size array
>  - dropped all patches already merged
>
> Changes since v1:
>  - rebased to v5.12-rc1
>  - a few more cleanups
>  - merge and forward port the patch from Claire to move all the global
>    variables into a struct to prepare for multiple instances