linux-kernel - Re: [RFC, PATCH 00/12] TDX: Enable Dynamic PAMT

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Message-ID: <hwxaujzu4jz5v4gztv2afbfzrqhldh3aq42jbpi2owussor46y@v2vfzrybtdnx>
Date: Thu, 15 May 2025 19:02:27 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Sean Christopherson <seanjc@...gle.com>, pbonzini@...hat.com, 
	rick.p.edgecombe@...el.com, isaku.yamahata@...el.com, kai.huang@...el.com, 
	yan.y.zhao@...el.com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, 
	dave.hansen@...ux.intel.com, kvm@...r.kernel.org, x86@...nel.org, linux-coco@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [RFC, PATCH 00/12] TDX: Enable Dynamic PAMT

On Thu, May 15, 2025 at 08:03:28AM -0700, Dave Hansen wrote:
> On 5/15/25 07:22, Kirill A. Shutemov wrote:
> > VMM is responsible for allocating and freeing PAMT_4K. There's a pair of
> > new SEAMCALLs for it: TDH.PHYMEM.PAMT.ADD and TDH.PHYMEM.PAMT.REMOVE. They
> > add/remove PAMT memory in form of page pair. There's no requirement for
> > these pages to be contiguous.
> 
> BTW, that second sentence is a little goofy. Is it talking about
> ADD/REMOVE being a matched pair? Or that there needs to be 8k of
> metadata storage provided to each ADD/REMOVE call?

Both :P

Pair of SEAMCALLs operate on pairs of pages.

> One thing I've noticed in writing changelogs and so forth is that
> repetition can hurt understanding if the concepts aren't the same. Like
> saying there is a "pair" of calls and a "pair" of pages when the fact
> that both are pairs is a coincidence rather than an intentional and
> important part of the design.

Yeah, I see it.

I will try to avoid to "pair" for SEAMCALLs in Dynamic PAMT context.
Maybe it will clear up the confusion.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov