linux-kernel - Re: [PATCH v19 010/130] KVM: x86: Pass is_private to gmem hook of gmem_max

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Date: Fri, 19 Apr 2024 09:19:29 +0800
From: Yan Zhao <yan.y.zhao@...el.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 v19 010/130] KVM: x86: Pass is_private to gmem hook of
 gmem_max_level

On Mon, Feb 26, 2024 at 12:25:12AM -0800, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
> 
> TDX wants to know the faulting address is shared or private so that the max
> level is limited by Secure-EPT or not.  Because fault->gfn doesn't include
> shared bit, gfn doesn't tell if the faulting address is shared or not.
> Pass is_private for TDX case.
> 
> TDX logic will be if (!is_private) return 0; else return PG_LEVEL_4K.
> 
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>  arch/x86/include/asm/kvm_host.h | 3 ++-
>  arch/x86/kvm/mmu/mmu.c          | 3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index d15f5b4b1656..57ce89fc2740 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1797,7 +1797,8 @@ struct kvm_x86_ops {
>  
>  	gva_t (*get_untagged_addr)(struct kvm_vcpu *vcpu, gva_t gva, unsigned int flags);
>  
> -	int (*gmem_max_level)(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, u8 *max_level);
> +	int (*gmem_max_level)(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn,
> +			      bool is_private, u8 *max_level);
>  };
>  
>  struct kvm_x86_nested_ops {
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 1e5e12d2707d..22db1a9f528a 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4324,7 +4324,8 @@ static int kvm_faultin_pfn_private(struct kvm_vcpu *vcpu,
>  
>  	max_level = kvm_max_level_for_order(max_order);
>  	r = static_call(kvm_x86_gmem_max_level)(vcpu->kvm, fault->pfn,
> -						fault->gfn, &max_level);
> +						fault->gfn, fault->is_private,
> +						&max_level);
fault->is_private is always true in kvm_faultin_pfn_private().
Besides, as shared page allocation will not go to kvm_faultin_pfn_private(),
why do we need to add the "is_private" parameter ?

>  	if (r) {
>  		kvm_release_pfn_clean(fault->pfn);
>  		return r;
> -- 
> 2.25.1
> 
>