Re: [PATCH v7 06/11] KVM: TDX: Allocate PAMT memory for TD and vCPU control structures

On Fri, Jul 17, 2026, Rick Edgecombe wrote:
> From: "Kirill A. Shutemov" <[email protected]>
> 
> Use control page helpers for allocating and freeing TD control structures,
> such that 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 ensure PAMT backing is installed
> for any 4KB page being gifted to the TDX module, and must tear down the
> backing when all associated gifted pages are 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.
> 
> Signed-off-by: Kirill A. Shutemov <[email protected]>
> [sean: handle alloc+free+reclaim in one patch]
> Signed-off-by: Sean Christopherson <[email protected]>
> [rick: enhance log, reviewing, rebase, with help from AI tooling]
> Signed-off-by: Rick Edgecombe <[email protected]>
> Reviewed-by: Binbin Wu <[email protected]>
> Reviewed-by: Chao Gao <[email protected]>
> Reviewed-by: Yan Zhao <[email protected]>
> Reviewed-by: Tony Lindgren <[email protected]>
> ---

Acked-by: Sean Christopherson <[email protected]>