Re: [PATCH v6 0/9] coco: guest: Enforce host page-size alignment for shared buffers

[Jason Gunthorpe]

On Fri, Sep 18, 2026 at 05:52:31PM +0100, Catalin Marinas wrote:

> TBH, I'm tempted not to support this configuration at all, just fail
> gracefully if the realm page size doesn't match the host's. However, if
> that's a real world configuration, 

realm != host is going to be fairly common.

host > realm is probably not that common, I would guess.

> I wonder whether could we leverage the swiotlb mechanism but with a
> separate io_tlb_mem as a shared coco allocator with the right
> alignment and use this pool when force_dma_unencrypted() instead of
> specific alloc_pages() with adjusted order.

I propose we fix the far too low level set memory decrypted apis into
proper allocators, with APIs that can handle a round up. Then see
where we end up after that.

If we can hide 90% of it in an allocator then lets see if we can open
code the rest.

Jason