Re: [PATCH v6 07/11] KVM: TDX: Allocate PAMT memory for TD and vCPU control structures

[Edgecombe, Rick P]

On Mon, 2026-07-06 at 16:47 -0700, Sean Christopherson wrote:
> On Mon, May 25, 2026, Rick Edgecombe wrote:
> > From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> > 
> > Use control page helpers for allocating and freeing TD control structures,
> > such these operations can work for Dynamic PAMT.
> > 
> > The TDX module tracks some state for each page of physical memory that it
> > might use. It calls this state the PAMT. It includes separate state for
> > each page size a physical page could be utilized at within the TDX module
> > (1GB, 2MB, 4KB). In Dynamic PAMT, only the 4KB page size state is
> > allocated dynamically. So the kernel must install PAMT backing for each 4KB
> > page before gifting it to the TDX module, and tear it down after the page
> > is reclaimed.
> > 
> > TD-scoped control pages (TDR, TDCS) and vCPU-scoped control pages (TDVPR,
> > TDCX) are all handed to the TDX module at 4KB page size and are therefore
> > subject to this requirement. Replace the raw alloc_page()/__free_page()
> > calls for these pages with tdx_alloc/free_control_page().
> > 
> > Switching between special Dynamic PAMT operations or normal page
> > alloc/free operations is handled internally in
> > tdx_alloc/free_control_page(). So don't check for Dynamic PAMT around these
> > calls. Just call them unconditionally. Similarly, drop the NULL checks
> > before freeing, as tdx_free_control_page() handles NULL internally.
> > 
> > No functional change intended when Dynamic PAMT is not in use.
> > 
> > Assisted-by: GitHub Copilot:claude-opus-4-6 Claude:claude-opus-4-7
> 
> Exactly what assistance was given, and when?  I certainly didn't use any of these
> tools, and given that Claude Opus 4.6 was released after I posted the v5 RFC, I
> doubt Kirill did either.

On this patch specifically, lots of "review this patch" type experiments IIRC.
Probably mostly around the log.

> 
> And in my strong opinion, even if AI tooling was used to rebase the patches, I
> don't think that level of "assistance" should be presented this way.  E.g. I would
> rather a more informal:
> 
>   [ Rick: enhance log, rebase with help from AI tooling]
> 
> Because unless I'm missing something, claiming that AI was used to write the patch
> is misleading and disingenuous.

Yea, I was just trying to follow the policy. It seems things are swinging the
other way now. This works.

> 
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> > [sean: handle alloc+free+reclaim in one patch]
> > Co-developed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> 
> Where did this come from?  I don't think me squashing two patches together
> warrants a Co-developed-by.

Gosh, I'm sorry. It looks like I added it. Will remove.

> 
> > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> > [Rick: enhance log]
> > Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>