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    SubjectRe: [PATCH v19 062/130] KVM: x86/tdp_mmu: Support TDX private mapping for TDP MMU
    On Mon, Feb 26, 2024 at 12:26:04AM -0800, isaku.yamahata@intel.com wrote:
    > From: Isaku Yamahata <isaku.yamahata@intel.com>
    >
    > @@ -1041,6 +1255,8 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
    > struct kvm *kvm = vcpu->kvm;
    > struct tdp_iter iter;
    > struct kvm_mmu_page *sp;
    > + gfn_t raw_gfn;
    > + bool is_private = fault->is_private && kvm_gfn_shared_mask(kvm);
    Why not put the checking of kvm_gfn_shared_mask() earlier before determining
    fault->is_private?
    e.g. in kvm_mmu_page_fault().

    > int ret = RET_PF_RETRY;
    >
    > kvm_mmu_hugepage_adjust(vcpu, fault);
    > @@ -1049,7 +1265,17 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
    >
    > rcu_read_lock();
    >
    > - tdp_mmu_for_each_pte(iter, mmu, fault->gfn, fault->gfn + 1) {
    > + raw_gfn = gpa_to_gfn(fault->addr);
    > +
    > + if (is_error_noslot_pfn(fault->pfn) ||
    The checking for noslot pfn is not required after this cleanup series [1] from
    Sean, right?

    > + !kvm_pfn_to_refcounted_page(fault->pfn)) {
    What's the purpose of rejecting non-refcounted page (which is useful for trusted
    IO)?

    Besides, looks pages are allocated via kvm_faultin_pfn_private() if
    fault->is_private, so where is the non-refcounted page from?


    > + if (is_private) {
    > + rcu_read_unlock();
    > + return -EFAULT;
    > + }
    > + }

    [1] https://lore.kernel.org/all/20240228024147.41573-1-seanjc@google.com/

    > + tdp_mmu_for_each_pte(iter, mmu, is_private, raw_gfn, raw_gfn + 1) {
    > int r;
    >
    > if (fault->nx_huge_page_workaround_enabled)
    ..

    > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
    > index d399009ef1d7..e27c22449d85 100644
    > --- a/virt/kvm/kvm_main.c
    > +++ b/virt/kvm/kvm_main.c
    > @@ -201,6 +201,7 @@ struct page *kvm_pfn_to_refcounted_page(kvm_pfn_t pfn)
    >
    > return NULL;
    > }
    > +EXPORT_SYMBOL_GPL(kvm_pfn_to_refcounted_page);
    >
    > /*
    > * Switches to specified vcpu, until a matching vcpu_put()
    > --
    > 2.25.1
    >
    >

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