Re: [PATCH v9 08/11] KVM: TDX: Get/put PAMT pages when (un)mapping private memory

[Vishal Annapurve]

On Wed, Aug 5, 2026 at 7:09 PM Rick Edgecombe
<rick.p.edgecombe@xxxxxxxxx> 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 2MB 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.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Co-developed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> [rick: enhance log, reviewing, rebase, with help from AI tooling]
> Co-developed-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
> Tested-by: Hongyu Ning <hongyu.ning@xxxxxxxxxxxxxxx>
> Reviewed-by: Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx>
> Reviewed-by: Tony Lindgren <tony.lindgren@xxxxxxxxxxxxxxx>
> Acked-by: Sohil Mehta <sohil.mehta@xxxxxxxxx>
> Acked-by: Sean Christopherson <seanjc@xxxxxxxxxx>

Reviewed-by: Vishal Annapurve <vannapurve@xxxxxxxxxx>