Re: [PATCH v4 06/17] KVM: x86/mmu: Allocate DPAMT pages for vCPU-induced page split

[Edgecombe, Rick P]

On Mon, 2026-09-28 at 17:10 +0800, Yan Zhao wrote:
> From: Sean Christopherson <seanjc@xxxxxxxxxx>
> 
> Extend the TDP MMU to allocate Dynamic PAMT backing pages (DPAMT pages) for
> vCPU-induced huge page splits in mirror roots when DPAMT is enabled.
> 
> Leverage the .topup_external_cache() interface to topup the DPAMT cache
> when allocating a new child page table for splitting. The DPAMT cache is
> currently a per-vCPU thread-local list. When a vCPU-induced page split
> occurs, DPAMT pages can be drawn locklessly from the list.
> 
> Pass min_nr_spts as 1 to .topup_external_cache(), indicating there's one
> new S-EPT page table page. So, tdx_topup_external_pamt_cache() will
> allocate DPAMT page pairs for both the newly added S-EPT page table page
> and the demoted guest private page.
> 
> tdp_mmu_alloc_sp_for_split() is currently not reachable from a non-vCPU
> context for mirror roots, since dirty page tracking is not yet allowed on
> mirror roots. So, simply add a WARN if tdx_topup_external_pamt_cache() is
> invoked under a non-vCPU context.
> 
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> Signed-off-by: Yan Zhao <yan.y.zhao@xxxxxxxxx>
> ---
> v4: new patch.

New? It is essentially this with a new log, right?
https://lore.kernel.org/kvm/20260129011517.3545883-39-seanjc@xxxxxxxxxx/#t

Reviewed-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>