linux-kernel - Re: [RFC PATCH v5 021/104] KVM: x86: Introduce hooks to free VM callback prezap and vm

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Date:   Tue, 5 Apr 2022 14:40:58 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...il.com, Jim Mattson <jmattson@...gle.com>,
        erdemaktas@...gle.com, Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC PATCH v5 021/104] KVM: x86: Introduce hooks to free VM
 callback prezap and vm_free

On 3/4/22 20:48, isaku.yamahata@...el.com wrote:
> From: Kai Huang <kai.huang@...el.com>
> 
> Before tearing down private page tables, TDX requires some resources of the
> guest TD to be destroyed (i.e. keyID must have been reclaimed, etc).  Add
> prezap callback before tearing down private page tables for it.
> 
> TDX needs to free some resources after other resources (i.e. vcpu related
> resources).  Add vm_free callback at the end of kvm_arch_destroy_vm().
> 
> Signed-off-by: Kai Huang <kai.huang@...el.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>   arch/x86/include/asm/kvm-x86-ops.h | 2 ++
>   arch/x86/include/asm/kvm_host.h    | 2 ++
>   arch/x86/kvm/x86.c                 | 8 ++++++++
>   3 files changed, 12 insertions(+)
> 
> diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
> index 8125d43d3566..ef48dcc98cfc 100644
> --- a/arch/x86/include/asm/kvm-x86-ops.h
> +++ b/arch/x86/include/asm/kvm-x86-ops.h
> @@ -20,7 +20,9 @@ KVM_X86_OP(has_emulated_msr)
>   KVM_X86_OP(vcpu_after_set_cpuid)
>   KVM_X86_OP(is_vm_type_supported)
>   KVM_X86_OP(vm_init)
> +KVM_X86_OP_NULL(mmu_prezap)
>   KVM_X86_OP_NULL(vm_destroy)
> +KVM_X86_OP_NULL(vm_free)
>   KVM_X86_OP(vcpu_create)
>   KVM_X86_OP(vcpu_free)
>   KVM_X86_OP(vcpu_reset)
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 8de357a9ad30..5ff7a0fba311 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1326,7 +1326,9 @@ struct kvm_x86_ops {
>   	bool (*is_vm_type_supported)(unsigned long vm_type);
>   	unsigned int vm_size;
>   	int (*vm_init)(struct kvm *kvm);
> +	void (*mmu_prezap)(struct kvm *kvm);
>   	void (*vm_destroy)(struct kvm *kvm);
> +	void (*vm_free)(struct kvm *kvm);
>   
>   	/* Create, but do not attach this VCPU */
>   	int (*vcpu_create)(struct kvm_vcpu *vcpu);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index f6438750d190..a48f5c69fadb 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -11779,6 +11779,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
>   	kvm_page_track_cleanup(kvm);
>   	kvm_xen_destroy_vm(kvm);
>   	kvm_hv_destroy_vm(kvm);
> +	static_call_cond(kvm_x86_vm_free)(kvm);
>   }
>   
>   static void memslot_rmap_free(struct kvm_memory_slot *slot)
> @@ -12036,6 +12037,13 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
>   
>   void kvm_arch_flush_shadow_all(struct kvm *kvm)
>   {
> +	/*
> +	 * kvm_mmu_zap_all() zaps both private and shared page tables.  Before
> +	 * tearing down private page tables, TDX requires some TD resources to
> +	 * be destroyed (i.e. keyID must have been reclaimed, etc).  Invoke
> +	 * kvm_x86_mmu_prezap() for this.
> +	 */
> +	static_call_cond(kvm_x86_mmu_prezap)(kvm);
>   	kvm_mmu_zap_all(kvm);

Please rename the hook to (*flush_shadow_all_private).

Otherwise ok,

Paolo

>   }
>