Re: [PATCH v6 09/11] KVM: TDX: Get/put PAMT pages when (un)mapping private memory

[Chao Gao]

On Mon, May 25, 2026 at 07:35:13PM -0700, Rick Edgecombe wrote:
>From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
>
>Add Dynamic PAMT support to KVM's S-EPT MMU by "getting" a PAMT page when
>adding guest memory (PAGE.ADD or PAGE.AUG), and "putting" the page when
>removing guest memory (PAGE.REMOVE).
>
>To access the per-vCPU PAMT caches without plumbing @vcpu throughout the
>TDP MMU, begrudgingly use kvm_get_running_vcpu() to get the vCPU, and bug
>the VM if KVM attempts to set an S-EPT leaf without an active vCPU.  KVM
>only supports creating _new_ mappings in page (pre)fault paths, all of
>which require an active vCPU.
>
>The PAMT memory holds metadata for TDX-protected memory. With Dynamic
>PAMT, PAMT_4K is allocated on demand. The kernel supplies the TDX module
>with a few pages that cover 2M of host physical memory.
>
>Releases are balanced via tdx_pamt_put(): every control-page free goes
>through tdx_free_control_page(), and guest data pages are put directly on
>the successful tdh_mem_page_remove() path and in the
>tdx_mem_page_add/aug() error path.
>
>Assisted-by: Sashiko:claude-opus-4-6 GitHub Copilot:claude-opus-4-6 Claude:claude-opus-4-7
>Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
>Co-developed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
>Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
>Co-developed-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
>Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
>---
>v6:
> - Don't have topup op take a min param (Yan, Sean)

The topup_external_cache x86 op still takes int min_nr_spts. Did you
forget to remove it, or am I misreading this changelog?