linux-kernel - Re: [RFC PATCH 02/21] x86/virt/tdx: Enhance tdh_mem_page

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Message-ID: <CAGtprH8jTnuHtx1cMOT541r3igNA6=LbguXeJJOzzChYU_099Q@mail.gmail.com>
Date: Tue, 8 Jul 2025 08:29:47 -0700
From: Vishal Annapurve <vannapurve@...gle.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
Cc: "pbonzini@...hat.com" <pbonzini@...hat.com>, "seanjc@...gle.com" <seanjc@...gle.com>, 
	"Zhao, Yan Y" <yan.y.zhao@...el.com>, "Shutemov, Kirill" <kirill.shutemov@...el.com>, 
	"quic_eberman@...cinc.com" <quic_eberman@...cinc.com>, "Li, Xiaoyao" <xiaoyao.li@...el.com>, 
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "Hansen, Dave" <dave.hansen@...el.com>, 
	"david@...hat.com" <david@...hat.com>, "thomas.lendacky@....com" <thomas.lendacky@....com>, 
	"tabba@...gle.com" <tabba@...gle.com>, "Li, Zhiquan1" <zhiquan1.li@...el.com>, "Du, Fan" <fan.du@...el.com>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"michael.roth@....com" <michael.roth@....com>, "Weiny, Ira" <ira.weiny@...el.com>, 
	"vbabka@...e.cz" <vbabka@...e.cz>, "binbin.wu@...ux.intel.com" <binbin.wu@...ux.intel.com>, 
	"ackerleytng@...gle.com" <ackerleytng@...gle.com>, "Yamahata, Isaku" <isaku.yamahata@...el.com>, 
	"Peng, Chao P" <chao.p.peng@...el.com>, "jroedel@...e.de" <jroedel@...e.de>, 
	"Miao, Jun" <jun.miao@...el.com>, "pgonda@...gle.com" <pgonda@...gle.com>, 
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: [RFC PATCH 02/21] x86/virt/tdx: Enhance tdh_mem_page_aug() to
 support huge pages

On Tue, Jul 8, 2025 at 6:56 AM Edgecombe, Rick P
<rick.p.edgecombe@...el.com> wrote:
>
> On Tue, 2025-07-08 at 16:48 +0800, Yan Zhao wrote:
> > On Thu, Apr 24, 2025 at 11:04:28AM +0800, Yan Zhao wrote:
> > > diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> > > index f5e2a937c1e7..a66d501b5677 100644
> > > --- a/arch/x86/virt/vmx/tdx/tdx.c
> > > +++ b/arch/x86/virt/vmx/tdx/tdx.c
> > > @@ -1595,9 +1595,18 @@ u64 tdh_mem_page_aug(struct tdx_td *td, u64 gpa, int level, struct page *page, u
> > According to the discussion in DPAMT [*],
> > "hpa here points to a 2M region that pamt_pages covers. We don't have
> > struct page that represents it. Passing 4k struct page would be
> > misleading IMO."
> >
> > Should we update tdh_mem_page_aug() accordingly to use hpa?
> > Or use struct folio instead?
> >
> > [*] https://lore.kernel.org/all/3coaqkcfp7xtpvh2x4kph55qlopupknm7dmzqox6fakzaedhem@a2oysbvbshpm/
>
> The original seamcall wrapper patches used "u64 hpa", etc everywhere. The
> feedback was that it was too error prone to not have types. We looked at using
> kvm types (hpa_t, etc), but the type checking was still just surface level [0].
>
> So the goal is to reduce errors and improve code readability. We can consider
> breaking symmetry if it is better that way. In this case though, why not use
> struct folio?

My vote would be to prefer using "hpa" and not rely on folio/page
structs for guest_memfd allocated memory wherever possible.

>
> [0] https://lore.kernel.org/kvm/30d0cef5-82d5-4325-b149-0e99833b8785@intel.com/