Re: [PATCH v2 04/31] x86/virt/tdx: Support allocating contiguous pages for tdx_page_array

[Dan Williams <djbw@kernel.org>]

Xu Yilun wrote:
> The current tdx_page_array implementation allocates scattered order-0
> pages. However, some TDX Module operations benefit from contiguous
> physical memory. E.g. Enabling TDX Module Extensions (an optional TDX
> feature) requires ~50MB memory and never returns. Such allocation
> would at worst cause ~25GB permanently fragmented memory if each
> allocated page is from a different 2M region.
> 
> Support allocating contiguous pages for tdx_page_array by making the
> allocation method configurable. Change the tdx_page_array_alloc() to
> accept a custom allocation function pointer and a context parameter.
> Wrap the specific allocation into a tdx_page_array_alloc_contig()
> helper.
> 
> The foreseeable caller will allocate ~50MB memory with this helper,
> exceeding the maximum HPAs (512) a root page can hold, the typical usage
> will be:
> 
>  - struct tdx_page_array *array = tdx_page_array_alloc_contig(nr_pages);
>  - for each 512-page bulk
>    - tdx_page_array_populate(array, offset);
>    - seamcall(TDH_XXX_ADD, array, ...);
> 
> The configurable allocation method would also benefit more
> tdx_page_array usages. TDX Module may require more specific memory
> layouts encoded in the root page. Will introduce them in following
> patches.

Will skip this one as I see it gets massively reworked in your
incremental update. The change to make the caller responsible for
creating the page array is great.