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, 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?

Probably?

I assume you're asking in the context of in-place conversion, where KVM will
allow a single guest_memfd page to be both the source and the dest?

Right now, KVM requires the source page to be a GUP'able page, specifically so
that KVM can obtain a reference and ensure the page isn't freed until KVM is done
with it.  If/when the source and dest are one and the same, then I don't think
we'd want to GUP the page (and there would be no need to since this would all run
while holding gmem's filemap_invalidate_lock()), at which point, yeah, passing a
"struct page" doesn't make much sense, and passing kvm_pfn_t or u64 or whatever
seems like the obvious choice.