Re: [PATCH 1/2] x86/virt/tdx: Use PFN directly for mapping guest private memory

[Sean Christopherson <seanjc@google.com>]

On Thu, Apr 02, 2026, Rick P Edgecombe wrote:
> On Thu, 2026-04-02 at 16:23 -0700, Ackerley Tng wrote:
> > Yan Zhao <yan.y.zhao@intel.com> writes:
> > 
> > > 
> > > [...snip...]
> > > 
> > > -u64 tdh_mem_page_add(struct tdx_td *td, u64 gpa, struct page *page, struct page *source, u64 *ext_err1, u64 *ext_err2)
> > > +u64 tdh_mem_page_add(struct tdx_td *td, u64 gpa, kvm_pfn_t pfn, struct page *source,
> > > +		     u64 *ext_err1, u64 *ext_err2)
> > >   {
> > >   	struct tdx_module_args args = {
> > >   		.rcx = gpa,
> > >   		.rdx = tdx_tdr_pa(td),
> > > -		.r8 = page_to_phys(page),
> > > +		.r8 = PFN_PHYS(pfn),
> > >   		.r9 = page_to_phys(source),
> > 
> > Perhaps in some future patch, are we considering also passing pfn
> > instead of struct page for source? Would we also update
> > kvm_tdx->page_add_src to be a kvm_pfn_t?
> 
> Can you remind me, with the new API we were going to do an in-place add right?
> Then I'd wonder if we could maybe change tdh_mem_page_add() to only have a
> single pfn arg.

No.  In-place ADD will be supported, but it won't be mandatory.  Practically
speaking, we can't make it mandatory unless we're willing to completely rip out
support for per-VM attributes (or at least, per-VM PRIVATE tracking).  I suppose
we could require in-place ADD when using per-gmem attributes, but I don't see
the point given that TDH_MEM_PAGE_ADD itself takes a source and dest.