Re: [PATCH] x86/virt/tdx: Use precalculated TDVPR page physical address

Dave Hansen
2025-10-20T15:10:44Z

On 10/20/25 07:42, Sean Christopherson wrote:
>> In a perfect world, we'd have sparse annotations for the vaddr, paddr,
>> pfn, dma_addr_t and all the other address spaces. Until then, I like
>> passing struct page around.
> But that clearly doesn't work since now the raw paddr is being passed in many
> places, and we end up with goofy code like this where one param takes a raw paddr,
> and another uses page_to_phys().
>
> @@ -1583,7 +1578,7 @@ u64 tdh_vp_addcx(struct tdx_vp *vp, struct page *tdcx_page)
> {
> struct tdx_module_args args = {
> .rcx = page_to_phys(tdcx_page),
> - .rdx = tdx_tdvpr_pa(vp),
> + .rdx = vp->tdvpr_pa,
> };

I'm kinda dense normally and my coffee hasn't kicked in yet. What
clearly does not work there?

Yeah, vp->tdvpr_pa is storing a physical address as a raw u64 and not a
'struct page'. That's not ideal. But it's also for a pretty good reason.

The "use 'struct page *' instead of u64 for physical addresses" thingy
is a good pattern, not an absolute rule. Use it when you can, but
abandon it for the greater good when necessary.

I don't hate the idea of a tdx_page_t. I'm just not sure it's worth the
trouble. I'd certainly take a good look at the patches if someone hacked
it together.