linux-kernel - Re: [PATCH v18 046/121] KVM: x86/mmu: Add a new is_private member for union kvm_mmu_page

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Date: Mon, 29 Jan 2024 09:50:13 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: isaku.yamahata@...el.com
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
 isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
 erdemaktas@...gle.com, Sean Christopherson <seanjc@...gle.com>,
 Sagi Shahar <sagis@...gle.com>, Kai Huang <kai.huang@...el.com>,
 chen.bo@...el.com, hang.yuan@...el.com, tina.zhang@...el.com
Subject: Re: [PATCH v18 046/121] KVM: x86/mmu: Add a new is_private member for
 union kvm_mmu_page_role



On 1/23/2024 7:53 AM, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
>
> Because TDX support introduces private mapping, add a new member in union
> kvm_mmu_page_role with access functions to check the member.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>   arch/x86/include/asm/kvm_host.h | 27 +++++++++++++++++++++++++++
>   arch/x86/kvm/mmu/mmu_internal.h |  5 +++++
>   arch/x86/kvm/mmu/spte.h         |  6 ++++++
>   3 files changed, 38 insertions(+)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 313519edd79e..0cdbbc21136b 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -349,7 +349,12 @@ union kvm_mmu_page_role {
>   		unsigned ad_disabled:1;
>   		unsigned guest_mode:1;
>   		unsigned passthrough:1;
> +#ifdef CONFIG_KVM_MMU_PRIVATE
> +		unsigned is_private:1;
> +		unsigned :4;
> +#else
>   		unsigned :5;
> +#endif
>   
>   		/*
>   		 * This is left at the top of the word so that
> @@ -361,6 +366,28 @@ union kvm_mmu_page_role {
>   	};
>   };
>   
> +#ifdef CONFIG_KVM_MMU_PRIVATE
> +static inline bool kvm_mmu_page_role_is_private(union kvm_mmu_page_role role)
> +{
> +	return !!role.is_private;
> +}
> +
> +static inline void kvm_mmu_page_role_set_private(union kvm_mmu_page_role *role)
> +{
> +	role->is_private = 1;
> +}
> +#else
> +static inline bool kvm_mmu_page_role_is_private(union kvm_mmu_page_role role)
> +{
> +	return false;
> +}
> +
> +static inline void kvm_mmu_page_role_set_private(union kvm_mmu_page_role *role)
> +{
> +	WARN_ON_ONCE(1);
> +}
> +#endif
> +
>   /*
>    * kvm_mmu_extended_role complements kvm_mmu_page_role, tracking properties
>    * relevant to the current MMU configuration.   When loading CR0, CR4, or EFER,
> diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
> index 2b9377442927..97af4e39ce6f 100644
> --- a/arch/x86/kvm/mmu/mmu_internal.h
> +++ b/arch/x86/kvm/mmu/mmu_internal.h
> @@ -145,6 +145,11 @@ 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_private_sp(const struct kvm_mmu_page *sp)
> +{
> +	return kvm_mmu_page_role_is_private(sp->role);
> +}
> +
>   static inline bool kvm_mmu_page_ad_need_write_protect(struct kvm_mmu_page *sp)
>   {
>   	/*
> diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
> index 1a163aee9ec6..88db32cba0fd 100644
> --- a/arch/x86/kvm/mmu/spte.h
> +++ b/arch/x86/kvm/mmu/spte.h
> @@ -264,6 +264,12 @@ static inline struct kvm_mmu_page *root_to_sp(hpa_t root)
>   	return spte_to_child_sp(root);
>   }
>   
> +static inline bool is_private_sptep(u64 *sptep)
> +{
> +	WARN_ON_ONCE(!sptep);

If sptep is NULL, should return here, otherwise, the following code will
de-reference a illegal pointer.

> +	return is_private_sp(sptep_to_sp(sptep));
> +}
> +
>   static inline bool is_mmio_spte(struct kvm *kvm, u64 spte)
>   {
>   	return (spte & shadow_mmio_mask) == kvm->arch.shadow_mmio_value &&