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References: <20240530210714.364118-1-rick.p.edgecombe@intel.com> <20240530210714.364118-5-rick.p.edgecombe@intel.com>
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From: Paolo Bonzini <pbonzini@redhat.com>
Date: Thu, 6 Jun 2024 18:06:33 +0200
Message-ID: <CABgObfa1xtZkGizNf=YrMYSo29v==qijMQJ-mZvobniS6-7OLw@mail.gmail.com>
Subject: Re: [PATCH v2 04/15] KVM: x86/mmu: Add a new mirror_pt member for
 union kvm_mmu_page_role
To: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: seanjc@google.com, kvm@vger.kernel.org, kai.huang@intel.com, 
	dmatlack@google.com, erdemaktas@google.com, isaku.yamahata@gmail.com, 
	linux-kernel@vger.kernel.org, sagis@google.com, yan.y.zhao@intel.com, 
	Isaku Yamahata <isaku.yamahata@intel.com>
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On Thu, May 30, 2024 at 11:07=E2=80=AFPM Rick Edgecombe
<rick.p.edgecombe@intel.com> wrote:
>
> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> Introduce a "mirror_pt" member to the kvm_mmu_page_role union to identify
> SPTEs associated with the mirrored EPT.
>
> The TDX module maintains the private half of the EPT mapped in the TD in
> its protected memory. KVM keeps a copy of the private GPAs in a mirrored
> EPT tree within host memory. This "mirror_pt" attribute enables vCPUs to
> find and get the root page of mirrored EPT from the MMU root list for a
> guest TD. This also allows KVM MMU code to detect changes in mirrored EPT
> according to the "mirror_pt" mmu page role and propagate the changes to
> the private EPT managed by TDX module.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> ---
> TDX MMU Prep v2:
>  - Rename private -> mirrored
>
> TDX MMU Prep:
> - Remove warning and NULL check in is_private_sptep() (Rick)
> - Update commit log (Yan)
>
> v19:
> - Fix is_private_sptep() when NULL case.
> - drop CONFIG_KVM_MMU_PRIVATE
> ---
>  arch/x86/include/asm/kvm_host.h | 13 ++++++++++++-
>  arch/x86/kvm/mmu/mmu_internal.h |  5 +++++
>  arch/x86/kvm/mmu/spte.h         |  5 +++++
>  3 files changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_h=
ost.h
> index 250899a0239b..084f4708aff1 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -351,7 +351,8 @@ union kvm_mmu_page_role {
>                 unsigned ad_disabled:1;
>                 unsigned guest_mode:1;
>                 unsigned passthrough:1;
> -               unsigned :5;
> +               unsigned mirror_pt:1;

"is_mirror".

> +               unsigned :4;
>
>                 /*
>                  * This is left at the top of the word so that
> @@ -363,6 +364,16 @@ union kvm_mmu_page_role {
>         };
>  };
>
> +static inline bool kvm_mmu_page_role_is_mirror(union kvm_mmu_page_role r=
ole)
> +{
> +       return !!role.mirror_pt;
> +}
> +
> +static inline void kvm_mmu_page_role_set_mirrored(union kvm_mmu_page_rol=
e *role)
> +{
> +       role->mirror_pt =3D 1;
> +}

Not needed, remove it.

>  /*
>   * kvm_mmu_extended_role complements kvm_mmu_page_role, tracking propert=
ies
>   * relevant to the current MMU configuration.   When loading CR0, CR4, o=
r EFER,
> diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_inter=
nal.h
> index faef40a561f9..6d82e389cd65 100644
> --- a/arch/x86/kvm/mmu/mmu_internal.h
> +++ b/arch/x86/kvm/mmu/mmu_internal.h
> @@ -157,6 +157,11 @@ static inline int kvm_mmu_page_as_id(struct kvm_mmu_=
page *sp)
>         return kvm_mmu_role_as_id(sp->role);
>  }
>
> +static inline bool is_mirror_sp(const struct kvm_mmu_page *sp)
> +{
> +       return kvm_mmu_page_role_is_mirror(sp->role);
> +}

e.g. "return sp->role.is_mirror".

>  static inline void *kvm_mmu_mirrored_spt(struct kvm_mmu_page *sp)
>  {
>         return sp->mirrored_spt;

This one is also unnecessary BTW.

Otherwise looks good.

Paolo

> diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
> index 5dd5405fa07a..b3c065280ba1 100644
> --- a/arch/x86/kvm/mmu/spte.h
> +++ b/arch/x86/kvm/mmu/spte.h
> @@ -265,6 +265,11 @@ static inline struct kvm_mmu_page *root_to_sp(hpa_t =
root)
>         return spte_to_child_sp(root);
>  }
>
> +static inline bool is_mirror_sptep(u64 *sptep)
> +{
> +       return is_mirror_sp(sptep_to_sp(sptep));
> +}
> +
>  static inline bool is_mmio_spte(struct kvm *kvm, u64 spte)
>  {
>         return (spte & shadow_mmio_mask) =3D=3D kvm->arch.shadow_mmio_val=
ue &&
> --
> 2.34.1
>