linux-kernel - Re: [RFC PATCH v2 03/23] x86/tdx: Enhance tdh_phymem_page_wbinvd

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Message-ID: <CAGtprH8zEKcyx_i7PRWd-fXWeuc+sDw7rMr1=zpgkbT-sfS6YA@mail.gmail.com>
Date: Tue, 9 Dec 2025 17:14:22 -0800
From: Vishal Annapurve <vannapurve@...gle.com>
To: Yan Zhao <yan.y.zhao@...el.com>
Cc: pbonzini@...hat.com, seanjc@...gle.com, linux-kernel@...r.kernel.org, 
	kvm@...r.kernel.org, x86@...nel.org, rick.p.edgecombe@...el.com, 
	dave.hansen@...el.com, kas@...nel.org, tabba@...gle.com, 
	ackerleytng@...gle.com, quic_eberman@...cinc.com, michael.roth@....com, 
	david@...hat.com, vbabka@...e.cz, thomas.lendacky@....com, pgonda@...gle.com, 
	zhiquan1.li@...el.com, fan.du@...el.com, jun.miao@...el.com, 
	ira.weiny@...el.com, isaku.yamahata@...el.com, xiaoyao.li@...el.com, 
	binbin.wu@...ux.intel.com, chao.p.peng@...el.com
Subject: Re: [RFC PATCH v2 03/23] x86/tdx: Enhance tdh_phymem_page_wbinvd_hkid()
 to invalidate huge pages

On Thu, Aug 7, 2025 at 2:42 AM Yan Zhao <yan.y.zhao@...el.com> wrote:
>
> index 0a2b183899d8..8eaf8431c5f1 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -1694,6 +1694,7 @@ static int tdx_sept_drop_private_spte(struct kvm *kvm, gfn_t gfn,
>  {
>         int tdx_level = pg_level_to_tdx_sept_level(level);
>         struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
> +       struct folio *folio = page_folio(page);
>         gpa_t gpa = gfn_to_gpa(gfn);
>         u64 err, entry, level_state;
>
> @@ -1728,8 +1729,9 @@ static int tdx_sept_drop_private_spte(struct kvm *kvm, gfn_t gfn,
>                 return -EIO;
>         }
>
> -       err = tdh_phymem_page_wbinvd_hkid((u16)kvm_tdx->hkid, page);
> -
> +       err = tdh_phymem_page_wbinvd_hkid((u16)kvm_tdx->hkid, folio,
> +                                         folio_page_idx(folio, page),
> +                                         KVM_PAGES_PER_HPAGE(level));

This code seems to assume that folio_order() always matches the level
at which it is mapped in the EPT entries. IIUC guest_memfd can decide
to split folios to 4K for the complete huge folio before zapping the
hugepage EPT mappings. I think it's better to just round the pfn to
the hugepage address based on the level they were mapped at instead of
relying on the folio order.