linux-kernel - Re: [PATCH v2 11/27] KVM: x86/mmu: Don't rely on page-track mechanism to flush on memslot change

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Message-ID: <ZBEanQaJTCkjcDOn@yzhao56-desk.sh.intel.com>
Date:   Wed, 15 Mar 2023 09:08:45 +0800
From:   Yan Zhao <yan.y.zhao@...el.com>
To:     Sean Christopherson <seanjc@...gle.com>
CC:     Paolo Bonzini <pbonzini@...hat.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhi Wang <zhi.a.wang@...el.com>, <kvm@...r.kernel.org>,
        <intel-gvt-dev@...ts.freedesktop.org>,
        <intel-gfx@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        Ben Gardon <bgardon@...gle.com>
Subject: Re: [PATCH v2 11/27] KVM: x86/mmu: Don't rely on page-track
 mechanism to flush on memslot change

On Fri, Mar 10, 2023 at 04:22:42PM -0800, Sean Christopherson wrote:
...
> -static void kvm_mmu_invalidate_zap_pages_in_memslot(struct kvm *kvm,
> -			struct kvm_memory_slot *slot,
> -			struct kvm_page_track_notifier_node *node)
> -{
> -	kvm_mmu_zap_all_fast(kvm);
> -}
> -
>  int kvm_mmu_init_vm(struct kvm *kvm)
>  {
>  	struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;
> @@ -6110,7 +6103,6 @@ int kvm_mmu_init_vm(struct kvm *kvm)
>  	}
>  
>  	node->track_write = kvm_mmu_pte_write;
> -	node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
>  	kvm_page_track_register_notifier(kvm, node);
>  
>  	kvm->arch.split_page_header_cache.kmem_cache = mmu_page_header_cache;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index f706621c35b8..29dd6c97d145 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -12662,6 +12662,8 @@ void kvm_arch_flush_shadow_all(struct kvm *kvm)
>  void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
>  				   struct kvm_memory_slot *slot)
>  {
> +	kvm_mmu_zap_all_fast(kvm);
Could we still call kvm_mmu_invalidate_zap_pages_in_memslot() here?
As I know, for TDX, its version of
kvm_mmu_invalidate_zap_pages_in_memslot() is like

static void kvm_mmu_invalidate_zap_pages_in_memslot(struct kvm *kvm,
                        struct kvm_memory_slot *slot,
                        struct kvm_page_track_notifier_node *node)
{
        if (kvm_gfn_shared_mask(kvm))
                kvm_mmu_zap_memslot(kvm, slot);
        else
                kvm_mmu_zap_all_fast(kvm);
}

Maybe this kind of judegment is better to be confined in mmu.c?

Thanks
Yan

> +
>  	kvm_page_track_flush_slot(kvm, slot);
>  }
>