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

[Chao Gao]

On Mon, May 25, 2026 at 07:35:11PM -0700, 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
>Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
>[sean: handle alloc+free+reclaim in one patch]
>Co-developed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
>Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
>[Rick: enhance log]
>Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>

Reviewed-by: Chao Gao <chao.gao@xxxxxxxxx>