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

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Message-ID: <aTjKV/hAEO4odtDQ@yzhao56-desk.sh.intel.com>
Date: Wed, 10 Dec 2025 09:18:15 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: Vishal Annapurve <vannapurve@...gle.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 Tue, Dec 09, 2025 at 05:14:22PM -0800, Vishal Annapurve wrote:
> 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.
I don't think so.
Please check the implemenation of tdh_phymem_page_wbinvd_hkid() [1].
Only npages=KVM_PAGES_PER_HPAGE(level) will be invalidated, while npages
<= folio_nr_pages(folio).

[1] https://lore.kernel.org/all/20250807094202.4481-1-yan.y.zhao@intel.com/

> 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.