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

[Kiryl Shutsemau <kas@kernel.org>]

On Thu, Mar 19, 2026 at 07:59:53PM +0800, Yan Zhao wrote:
> On Thu, Mar 19, 2026 at 10:39:14AM +0000, Kiryl Shutsemau wrote:
> > On Thu, Mar 19, 2026 at 08:57:03AM +0800, Yan Zhao wrote:
> > > @@ -1639,16 +1644,17 @@ u64 tdh_vp_addcx(struct tdx_vp *vp, struct page *tdcx_page)
> > >  }
> > >  EXPORT_SYMBOL_FOR_KVM(tdh_vp_addcx);
> > >  
> > > -u64 tdh_mem_page_aug(struct tdx_td *td, u64 gpa, int level, struct page *page, u64 *ext_err1, u64 *ext_err2)
> > > +u64 tdh_mem_page_aug(struct tdx_td *td, u64 gpa, int level, kvm_pfn_t pfn,
> > > +		     u64 *ext_err1, u64 *ext_err2)
> > >  {
> > >  	struct tdx_module_args args = {
> > >  		.rcx = gpa | level,
> > >  		.rdx = tdx_tdr_pa(td),
> > > -		.r8 = page_to_phys(page),
> > > +		.r8 = PFN_PHYS(pfn),
> > >  	};
> > >  	u64 ret;
> > >  
> > > -	tdx_clflush_page(page);
> > > +	tdx_clflush_pfn(pfn);
> > 
> > This is pre-existing problem, but shouldn't we respect @level here?
> > Flush size need to take page size into account.
> Hmm, flush size is fixed to PAGE_SIZE, because this series is based on the
> upstream code where huge page is not supported, so there's 
> "if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm))" in KVM.
> 
> Though tdh_mem_page_aug() is an API, it is currently only exported to KVM and
> uses type kvm_pfn_t. So, is it still acceptable to assume flush size to be
> PAGE_SIZE? Honoring level will soon be introduced by huge page patches.

It caught my eye because previously size to flush was passed down to
tdx_clflush_page() in the struct page (although never used there).
With switching to pfn, we give up this information and it has to be
passed separately. It would be easy to miss that in huge page patches,
if we don't pass down level here.

> 
> If you think it needs to be fixed before huge page series, what about fixing it
> in a separate cleanup patch? IMO, it would be better placed after Sean's cleanup
> patch [1], so we can use page_level_size() instead of inventing the wheel.

I am okay with a separate patch.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov