linux-kernel - Re: [RFC PATCH v2 19/23] KVM: TDX: Pass down pfn to split_external

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Message-ID: <6fc69050-bd96-401f-8226-947b94a1f027@linux.intel.com>
Date: Thu, 4 Sep 2025 16:30:44 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Yan Zhao <yan.y.zhao@...el.com>
Cc: pbonzini@...hat.com, seanjc@...gle.com, linux-kernel@...r.kernel.org,
 kvm@...r.kernel.org, x86@...nel.org, rick.p.edgecombe@...el.com,
 dave.hansen@...el.com, kas@...nel.org, tabba@...gle.com,
 ackerleytng@...gle.com, quic_eberman@...cinc.com, michael.roth@....com,
 david@...hat.com, vannapurve@...gle.com, vbabka@...e.cz,
 thomas.lendacky@....com, pgonda@...gle.com, zhiquan1.li@...el.com,
 fan.du@...el.com, jun.miao@...el.com, ira.weiny@...el.com,
 isaku.yamahata@...el.com, xiaoyao.li@...el.com, chao.p.peng@...el.com
Subject: Re: [RFC PATCH v2 19/23] KVM: TDX: Pass down pfn to
 split_external_spt()



On 8/7/2025 5:45 PM, Yan Zhao wrote:
> From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
>
> Pass down pfn to kvm_x86_ops::split_external_spt(). It is required for
> handling Dynamic PAMT in tdx_sept_split_private_spt().
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Signed-off-by: Yan Zhao <yan.y.zhao@...el.com>
> ---
> RFC v2:
> - Pulled from
>    git://git.kernel.org/pub/scm/linux/kernel/git/kas/linux.git tdx/dpamt-huge.
> - Rebased on top of TDX huge page RFC v2 (Yan)
> ---
>   arch/x86/include/asm/kvm_host.h | 3 ++-
>   arch/x86/kvm/mmu/tdp_mmu.c      | 6 +++++-
>   arch/x86/kvm/vmx/tdx.c          | 3 ++-
>   3 files changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 6cb5b422dd1d..6b6c46c27390 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1841,7 +1841,8 @@ struct kvm_x86_ops {
>   
>   	/* Split the external page table into smaller page tables */
>   	int (*split_external_spt)(struct kvm *kvm, gfn_t gfn, enum pg_level level,
> -				  void *external_spt, bool mmu_lock_shared);
> +				  kvm_pfn_t pfn_for_gfn, void *external_spt,
> +				  bool mmu_lock_shared);
>   
>   	bool (*has_wbinvd_exit)(void);
>   
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index 62a09a9655c3..eb758aaa4374 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -389,11 +389,15 @@ static int split_external_spt(struct kvm *kvm, gfn_t gfn, u64 old_spte,
>   			      u64 new_spte, int level, bool shared)
>   {
>   	void *external_spt = get_external_spt(gfn, new_spte, level);
> +	kvm_pfn_t pfn_for_gfn = spte_to_pfn(old_spte);
>   	int ret;
>   
>   	KVM_BUG_ON(!external_spt, kvm);
>   
> -	ret = kvm_x86_call(split_external_spt)(kvm, gfn, level, external_spt, shared);
> +	ret = kvm_x86_call(split_external_spt)(kvm, gfn, level,
> +					       pfn_for_gfn, external_spt,
> +					       shared);

It can save one line by moving "pfn_for_gfn" up.

> +
>   	return ret;
>   }
>   /**
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 71115058e5e6..24aa9aaad6d8 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -1941,7 +1941,8 @@ static int tdx_spte_demote_private_spte(struct kvm *kvm, gfn_t gfn,
>   }
>   
>   static int tdx_sept_split_private_spt(struct kvm *kvm, gfn_t gfn, enum pg_level level,
> -				      void *private_spt, bool mmu_lock_shared)
> +				      kvm_pfn_t pfn_for_gfn, void *private_spt,
> +				      bool mmu_lock_shared)
>   {
>   	struct page *page = virt_to_page(private_spt);
>   	int ret;