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References: <cover.1646422845.git.isaku.yamahata@intel.com> <7a5246c54427952728bd702bd7f2c6963eefa712.1646422845.git.isaku.yamahata@intel.com>
In-Reply-To: <7a5246c54427952728bd702bd7f2c6963eefa712.1646422845.git.isaku.yamahata@intel.com>
From:   Sagi Shahar <sagis@google.com>
Date:   Thu, 28 Apr 2022 17:28:18 -0700
Message-ID: <CAAhR5DE4-Z6JYLHbWyEyraqqWCx5bD+gZADAnisDmSJ4bkgV8g@mail.gmail.com>
Subject: Re: [RFC PATCH v5 048/104] KVM: x86/tdp_mmu: Support TDX private
 mapping for TDP MMU
To:     "Yamahata, Isaku" <isaku.yamahata@intel.com>
Cc:     kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        isaku.yamahata@gmail.com, Paolo Bonzini <pbonzini@redhat.com>,
        Jim Mattson <jmattson@google.com>,
        Erdem Aktas <erdemaktas@google.com>,
        Connor Kuehl <ckuehl@redhat.com>,
        Sean Christopherson <seanjc@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

 is not  .

On Fri, Mar 4, 2022 at 12:14 PM <isaku.yamahata@intel.com> wrote:
>
> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> Use private EPT to mirror Secure EPT, and On the change of the private EPT
> entry, invoke kvm_x86_ops hook in __handle_changed_spte() to propagate the
> change to Secure EPT.
>
> On EPT violation, determine which EPT to use, private or shared, based on
> faulted GPA.  When allocating an EPT page, record it (private or shared) in
> the page role.  The private is passed down to the function as an argument
> as necessary.  When the private EPT entry is changed, call the hook.
>
> When zapping EPT, the EPT entry is frozen with the special EPT value that
> clears the present bit. After the TLB shootdown, the entry is set to the
> eventual value.  On populating the EPT entry, atomically set the entry.
>
> For TDX, TDX SEAMCALL to update Secure EPT in addition to direct access to
> the private EPT entry.  For the zapping case, freeing the EPT entry
> works. It can call TDX SEAMCALL in addition to TLB shootdown.  For
> populating the private EPT entry, there can be a race condition without
> further protection
>
>   vcpu 1: populating 2M private EPT entry
>   vcpu 2: populating 4K private EPT entry
>   vcpu 2: TDX SEAMCALL to update 4K secure EPT => error
>   vcpu 1: TDX SEAMCALL to update 4M secure EPT
>
> To avoid the race, the frozen EPT entry is utilized.  Instead of atomic
> update of the private EPT entry, freeze the entry, call the hook that
> invokes TDX SEAMCALL, set the entry to the final value (unfreeze).
>
> Support 4K page only at this stage.  2M page support can be done in future
> patches.
>
> Co-developed-by: Kai Huang <kai.huang@intel.com>
> Signed-off-by: Kai Huang <kai.huang@intel.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
>  arch/x86/include/asm/kvm-x86-ops.h |   2 +
>  arch/x86/include/asm/kvm_host.h    |   8 +
>  arch/x86/kvm/mmu/mmu.c             |  31 +++-
>  arch/x86/kvm/mmu/tdp_iter.h        |   2 +-
>  arch/x86/kvm/mmu/tdp_mmu.c         | 226 +++++++++++++++++++++++------
>  arch/x86/kvm/mmu/tdp_mmu.h         |  13 +-
>  virt/kvm/kvm_main.c                |   1 +
>  7 files changed, 232 insertions(+), 51 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
> index ef48dcc98cfc..7e27b73d839f 100644
> --- a/arch/x86/include/asm/kvm-x86-ops.h
> +++ b/arch/x86/include/asm/kvm-x86-ops.h
> @@ -91,6 +91,8 @@ KVM_X86_OP(set_tss_addr)
>  KVM_X86_OP(set_identity_map_addr)
>  KVM_X86_OP(get_mt_mask)
>  KVM_X86_OP(load_mmu_pgd)
> +KVM_X86_OP(free_private_sp)
> +KVM_X86_OP(handle_changed_private_spte)
>  KVM_X86_OP_NULL(has_wbinvd_exit)
>  KVM_X86_OP(get_l2_tsc_offset)
>  KVM_X86_OP(get_l2_tsc_multiplier)
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 0c8cc7d73371..8406f8b5ab74 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -433,6 +433,7 @@ struct kvm_mmu {
>                          struct kvm_mmu_page *sp);
>         void (*invlpg)(struct kvm_vcpu *vcpu, gva_t gva, hpa_t root_hpa);
>         hpa_t root_hpa;
> +       hpa_t private_root_hpa;
>         gpa_t root_pgd;
>         union kvm_mmu_role mmu_role;
>         u8 root_level;
> @@ -1433,6 +1434,13 @@ struct kvm_x86_ops {
>         void (*load_mmu_pgd)(struct kvm_vcpu *vcpu, hpa_t root_hpa,
>                              int root_level);
>
> +       int (*free_private_sp)(struct kvm *kvm, gfn_t gfn, enum pg_level level,
> +                              void *private_sp);
> +       void (*handle_changed_private_spte)(
> +               struct kvm *kvm, gfn_t gfn, enum pg_level level,
> +               kvm_pfn_t old_pfn, bool was_present, bool was_leaf,
> +               kvm_pfn_t new_pfn, bool is_present, bool is_leaf, void *sept_page);
> +
>         bool (*has_wbinvd_exit)(void);
>
>         u64 (*get_l2_tsc_offset)(struct kvm_vcpu *vcpu);
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 8def8b97978f..0ec9548ff4dd 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3422,6 +3422,7 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
>  {
>         struct kvm_mmu *mmu = vcpu->arch.mmu;
>         u8 shadow_root_level = mmu->shadow_root_level;
> +       gfn_t gfn_stolen = kvm_gfn_stolen_mask(vcpu->kvm);
>         hpa_t root;
>         unsigned i;
>         int r;
> @@ -3432,7 +3433,11 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
>                 goto out_unlock;
>
>         if (is_tdp_mmu_enabled(vcpu->kvm)) {
> -               root = kvm_tdp_mmu_get_vcpu_root_hpa(vcpu);
> +               if (gfn_stolen && !VALID_PAGE(mmu->private_root_hpa)) {
> +                       root = kvm_tdp_mmu_get_vcpu_root_hpa(vcpu, true);
> +                       mmu->private_root_hpa = root;
> +               }
> +               root = kvm_tdp_mmu_get_vcpu_root_hpa(vcpu, false);
>                 mmu->root_hpa = root;
>         } else if (shadow_root_level >= PT64_ROOT_4LEVEL) {
>                 root = mmu_alloc_root(vcpu, 0, 0, shadow_root_level, true);
> @@ -5596,6 +5601,7 @@ static int __kvm_mmu_create(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
>         int i;
>
>         mmu->root_hpa = INVALID_PAGE;
> +       mmu->private_root_hpa = INVALID_PAGE;
>         mmu->root_pgd = 0;
>         for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
>                 mmu->prev_roots[i] = KVM_MMU_ROOT_INFO_INVALID;
> @@ -5772,6 +5778,10 @@ static void kvm_mmu_zap_all_fast(struct kvm *kvm)
>
>         write_unlock(&kvm->mmu_lock);
>
> +       /*
> +        * For now private root is never invalidate during VM is running,
> +        * so this can only happen for shared roots.
> +        */
>         if (is_tdp_mmu_enabled(kvm)) {
>                 read_lock(&kvm->mmu_lock);
>                 kvm_tdp_mmu_zap_invalidated_roots(kvm);
> @@ -5871,7 +5881,8 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
>         if (is_tdp_mmu_enabled(kvm)) {
>                 for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
>                         flush = kvm_tdp_mmu_zap_gfn_range(kvm, i, gfn_start,
> -                                                         gfn_end, flush);
> +                                                         gfn_end, flush,
> +                                                         false);
>         }
>
>         if (flush)
> @@ -5904,6 +5915,11 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm,
>                 write_unlock(&kvm->mmu_lock);
>         }
>
> +       /*
> +        * For now this can only happen for non-TD VM, because TD private
> +        * mapping doesn't support write protection.  kvm_tdp_mmu_wrprot_slot()
> +        * will give a WARN() if it hits for TD.
> +        */
>         if (is_tdp_mmu_enabled(kvm)) {
>                 read_lock(&kvm->mmu_lock);
>                 flush |= kvm_tdp_mmu_wrprot_slot(kvm, memslot, start_level);
> @@ -5952,6 +5968,9 @@ static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm,
>                 sp = sptep_to_sp(sptep);
>                 pfn = spte_to_pfn(*sptep);
>
> +               /* Private page dirty logging is not supported. */
> +               KVM_BUG_ON(is_private_spte(sptep), kvm);
> +
>                 /*
>                  * We cannot do huge page mapping for indirect shadow pages,
>                  * which are found on the last rmap (level = 1) when not using
> @@ -5992,6 +6011,11 @@ void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
>                 write_unlock(&kvm->mmu_lock);
>         }
>
> +       /*
> +        * This should only be reachable in case of log-dirty, wihch TD private
> +        * mapping doesn't support so far.  kvm_tdp_mmu_zap_collapsible_sptes()
> +        * internally gives a WARN() when it hits.
> +        */
>         if (is_tdp_mmu_enabled(kvm)) {
>                 read_lock(&kvm->mmu_lock);
>                 kvm_tdp_mmu_zap_collapsible_sptes(kvm, slot);
> @@ -6266,6 +6290,9 @@ int kvm_mmu_module_init(void)
>  void kvm_mmu_destroy(struct kvm_vcpu *vcpu)
>  {
>         kvm_mmu_unload(vcpu);
> +       if (is_tdp_mmu_enabled(vcpu->kvm))
> +               mmu_free_root_page(vcpu->kvm, &vcpu->arch.mmu->private_root_hpa,
> +                               NULL);
>         free_mmu_pages(&vcpu->arch.root_mmu);
>         free_mmu_pages(&vcpu->arch.guest_mmu);
>         mmu_free_memory_caches(vcpu);
> diff --git a/arch/x86/kvm/mmu/tdp_iter.h b/arch/x86/kvm/mmu/tdp_iter.h
> index e19cabbcb65c..ad22d5b691c5 100644
> --- a/arch/x86/kvm/mmu/tdp_iter.h
> +++ b/arch/x86/kvm/mmu/tdp_iter.h
> @@ -28,7 +28,7 @@ struct tdp_iter {
>         tdp_ptep_t pt_path[PT64_ROOT_MAX_LEVEL];
>         /* A pointer to the current SPTE */
>         tdp_ptep_t sptep;
> -       /* The lowest GFN mapped by the current SPTE */
> +       /* The lowest GFN (stolen bits included) mapped by the current SPTE */
>         gfn_t gfn;
>         /* The level of the root page given to the iterator */
>         int root_level;
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index a68f3a22836b..acba2590b51e 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -53,6 +53,11 @@ void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm)
>         rcu_barrier();
>  }
>
> +static gfn_t tdp_iter_gfn_unalias(struct kvm *kvm, struct tdp_iter *iter)
> +{
> +       return kvm_gfn_unalias(kvm, iter->gfn);
> +}
> +
>  static bool zap_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
>                           gfn_t start, gfn_t end, bool can_yield, bool flush,
>                           bool shared);
> @@ -175,10 +180,13 @@ static union kvm_mmu_page_role page_role_for_level(struct kvm_vcpu *vcpu,
>  }
>
>  static struct kvm_mmu_page *alloc_tdp_mmu_page(struct kvm_vcpu *vcpu, gfn_t gfn,
> -                                              int level)
> +                                              int level, bool private)
>  {
>         struct kvm_mmu_page *sp;
>
> +       WARN_ON(level != vcpu->arch.mmu->shadow_root_level &&
> +               kvm_is_private_gfn(vcpu->kvm, gfn) != private);
> +       WARN_ON(level == vcpu->arch.mmu->shadow_root_level && gfn != 0);
>         sp = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache);
>         sp->spt = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_shadow_page_cache);
>         set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
> @@ -186,14 +194,19 @@ static struct kvm_mmu_page *alloc_tdp_mmu_page(struct kvm_vcpu *vcpu, gfn_t gfn,
>         sp->role.word = page_role_for_level(vcpu, level).word;
>         sp->gfn = gfn;
>         sp->tdp_mmu_page = true;
> -       kvm_mmu_init_private_sp(sp);
> +
> +       if (private)
> +               kvm_mmu_alloc_private_sp(vcpu, sp);
> +       else
> +               kvm_mmu_init_private_sp(sp);
>
>         trace_kvm_mmu_get_page(sp, true);
>
>         return sp;
>  }
>
> -hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
> +static struct kvm_mmu_page *kvm_tdp_mmu_get_vcpu_root(struct kvm_vcpu *vcpu,
> +                                                     bool private)
>  {
>         union kvm_mmu_page_role role;
>         struct kvm *kvm = vcpu->kvm;
> @@ -206,11 +219,13 @@ hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
>         /* Check for an existing root before allocating a new one. */
>         for_each_tdp_mmu_root(kvm, root, kvm_mmu_role_as_id(role)) {
>                 if (root->role.word == role.word &&
> +                   is_private_sp(root) == private &&
>                     kvm_tdp_mmu_get_root(kvm, root))
>                         goto out;
>         }
>
> -       root = alloc_tdp_mmu_page(vcpu, 0, vcpu->arch.mmu->shadow_root_level);
> +       root = alloc_tdp_mmu_page(vcpu, 0, vcpu->arch.mmu->shadow_root_level,
> +                       private);
>         refcount_set(&root->tdp_mmu_root_count, 1);
>
>         spin_lock(&kvm->arch.tdp_mmu_pages_lock);
> @@ -218,12 +233,17 @@ hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
>         spin_unlock(&kvm->arch.tdp_mmu_pages_lock);
>
>  out:
> -       return __pa(root->spt);
> +       return root;
> +}
> +
> +hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu, bool private)
> +{
> +       return __pa(kvm_tdp_mmu_get_vcpu_root(vcpu, private)->spt);
>  }
>
>  static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
> -                               u64 old_spte, u64 new_spte, int level,
> -                               bool shared);
> +                               bool private_spte, u64 old_spte,
> +                               u64 new_spte, int level, bool shared);
>
>  static void handle_changed_spte_acc_track(u64 old_spte, u64 new_spte, int level)
>  {
> @@ -321,6 +341,7 @@ static void handle_removed_tdp_mmu_page(struct kvm *kvm, tdp_ptep_t pt,
>         int level = sp->role.level;
>         gfn_t base_gfn = sp->gfn;
>         int i;
> +       bool private_sp = is_private_sp(sp);
>
>         trace_kvm_mmu_prepare_zap_page(sp);
>
> @@ -370,7 +391,7 @@ static void handle_removed_tdp_mmu_page(struct kvm *kvm, tdp_ptep_t pt,
>                          */
>                         WRITE_ONCE(*sptep, SHADOW_REMOVED_SPTE);
>                 }
> -               handle_changed_spte(kvm, kvm_mmu_page_as_id(sp), gfn,
> +               handle_changed_spte(kvm, kvm_mmu_page_as_id(sp), gfn, private_sp,
>                                     old_child_spte, SHADOW_REMOVED_SPTE, level,
>                                     shared);
>         }
> @@ -378,6 +399,17 @@ static void handle_removed_tdp_mmu_page(struct kvm *kvm, tdp_ptep_t pt,
>         kvm_flush_remote_tlbs_with_address(kvm, base_gfn,
>                                            KVM_PAGES_PER_HPAGE(level + 1));
>
> +       if (private_sp &&
> +               WARN_ON(static_call(kvm_x86_free_private_sp)(
> +                               kvm, sp->gfn, sp->role.level,
> +                               kvm_mmu_private_sp(sp)))) {
> +               /*
> +                * Failed to unlink Secure EPT page and there is nothing to do
> +                * further.  Intentionally leak the page to prevent the kernel
> +                * from accessing the encrypted page.
> +                */
> +               kvm_mmu_init_private_sp(sp);
> +       }
>         call_rcu(&sp->rcu_head, tdp_mmu_free_sp_rcu_callback);
>  }
>
> @@ -386,6 +418,7 @@ static void handle_removed_tdp_mmu_page(struct kvm *kvm, tdp_ptep_t pt,
>   * @kvm: kvm instance
>   * @as_id: the address space of the paging structure the SPTE was a part of
>   * @gfn: the base GFN that was mapped by the SPTE
> + * @private_spte: the SPTE is private or not
>   * @old_spte: The value of the SPTE before the change
>   * @new_spte: The value of the SPTE after the change
>   * @level: the level of the PT the SPTE is part of in the paging structure
> @@ -397,14 +430,16 @@ static void handle_removed_tdp_mmu_page(struct kvm *kvm, tdp_ptep_t pt,
>   * This function must be called for all TDP SPTE modifications.
>   */
>  static void __handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
> -                                 u64 old_spte, u64 new_spte, int level,
> -                                 bool shared)
> +                                 bool private_spte, u64 old_spte,
> +                                 u64 new_spte, int level, bool shared)
>  {
>         bool was_present = is_shadow_present_pte(old_spte);
>         bool is_present = is_shadow_present_pte(new_spte);
>         bool was_leaf = was_present && is_last_spte(old_spte, level);
>         bool is_leaf = is_present && is_last_spte(new_spte, level);
> -       bool pfn_changed = spte_to_pfn(old_spte) != spte_to_pfn(new_spte);
> +       kvm_pfn_t old_pfn = spte_to_pfn(old_spte);
> +       kvm_pfn_t new_pfn = spte_to_pfn(new_spte);
> +       bool pfn_changed = old_pfn != new_pfn;
>
>         WARN_ON(level > PT64_ROOT_MAX_LEVEL);
>         WARN_ON(level < PG_LEVEL_4K);
> @@ -468,23 +503,49 @@ static void __handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
>
>         if (was_leaf && is_dirty_spte(old_spte) &&
>             (!is_present || !is_dirty_spte(new_spte) || pfn_changed))
> -               kvm_set_pfn_dirty(spte_to_pfn(old_spte));
> +               kvm_set_pfn_dirty(old_pfn);
> +
> +       /*
> +        * Special handling for the private mapping.  We are either
> +        * setting up new mapping at middle level page table, or leaf,
> +        * or tearing down existing mapping.
> +        */
> +       if (private_spte) {
> +               void *sept_page = NULL;
> +
> +               if (is_present && !is_leaf) {
> +                       struct kvm_mmu_page *sp = to_shadow_page(pfn_to_hpa(new_pfn));
> +
> +                       sept_page = kvm_mmu_private_sp(sp);
> +                       WARN_ON(!sept_page);
> +                       WARN_ON(sp->role.level + 1 != level);
> +                       WARN_ON(sp->gfn != gfn);
> +               }
> +
> +               static_call(kvm_x86_handle_changed_private_spte)(
> +                       kvm, gfn, level,
> +                       old_pfn, was_present, was_leaf,
> +                       new_pfn, is_present, is_leaf, sept_page);
> +       }
>
>         /*
>          * Recursively handle child PTs if the change removed a subtree from
>          * the paging structure.
>          */
> -       if (was_present && !was_leaf && (pfn_changed || !is_present))
> +       if (was_present && !was_leaf && (pfn_changed || !is_present)) {
> +               WARN_ON(private_spte !=
> +                       is_private_spte(spte_to_child_pt(old_spte, level)));
>                 handle_removed_tdp_mmu_page(kvm,
>                                 spte_to_child_pt(old_spte, level), shared);
> +       }
>  }
>
>  static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
> -                               u64 old_spte, u64 new_spte, int level,
> -                               bool shared)
> +                               bool private_spte, u64 old_spte, u64 new_spte,
> +                               int level, bool shared)
>  {
> -       __handle_changed_spte(kvm, as_id, gfn, old_spte, new_spte, level,
> -                             shared);
> +       __handle_changed_spte(kvm, as_id, gfn, private_spte,
> +                       old_spte, new_spte, level, shared);
>         handle_changed_spte_acc_track(old_spte, new_spte, level);
>         handle_changed_spte_dirty_log(kvm, as_id, gfn, old_spte,
>                                       new_spte, level);
> @@ -505,6 +566,10 @@ static inline bool tdp_mmu_set_spte_atomic(struct kvm *kvm,
>                                            struct tdp_iter *iter,
>                                            u64 new_spte)
>  {
> +       bool freeze_spte = is_private_spte(iter->sptep) &&
> +               !is_removed_spte(new_spte);
> +       u64 tmp_spte = freeze_spte ? SHADOW_REMOVED_SPTE : new_spte;
> +
>         WARN_ON_ONCE(iter->yielded);
>
>         lockdep_assert_held_read(&kvm->mmu_lock);
> @@ -521,13 +586,16 @@ static inline bool tdp_mmu_set_spte_atomic(struct kvm *kvm,
>          * does not hold the mmu_lock.
>          */
>         if (cmpxchg64(rcu_dereference(iter->sptep), iter->old_spte,
> -                     new_spte) != iter->old_spte)
> +                     tmp_spte) != iter->old_spte)
>                 return false;
>
> -       __handle_changed_spte(kvm, iter->as_id, iter->gfn, iter->old_spte,
> -                             new_spte, iter->level, true);
> +       __handle_changed_spte(kvm, iter->as_id, iter->gfn, is_private_spte(iter->sptep),
> +                             iter->old_spte, new_spte, iter->level, true);
>         handle_changed_spte_acc_track(iter->old_spte, new_spte, iter->level);
>
> +       if (freeze_spte)
> +               WRITE_ONCE(*rcu_dereference(iter->sptep), new_spte);
> +
>         return true;
>  }
>
> @@ -603,8 +671,8 @@ static inline void __tdp_mmu_set_spte(struct kvm *kvm, struct tdp_iter *iter,
>
>         WRITE_ONCE(*rcu_dereference(iter->sptep), new_spte);
>
> -       __handle_changed_spte(kvm, iter->as_id, iter->gfn, iter->old_spte,
> -                             new_spte, iter->level, false);
> +       __handle_changed_spte(kvm, iter->as_id, iter->gfn, is_private_spte(iter->sptep),
> +                             iter->old_spte, new_spte, iter->level, false);
>         if (record_acc_track)
>                 handle_changed_spte_acc_track(iter->old_spte, new_spte,
>                                               iter->level);
> @@ -644,9 +712,10 @@ static inline void tdp_mmu_set_spte_no_dirty_log(struct kvm *kvm,
>                         continue;                                       \
>                 else
>
> -#define tdp_mmu_for_each_pte(_iter, _mmu, _start, _end)                \
> -       for_each_tdp_pte(_iter, __va(_mmu->root_hpa),           \
> -                        _mmu->shadow_root_level, _start, _end)
> +#define tdp_mmu_for_each_pte(_iter, _mmu, _private, _start, _end)              \
> +       for_each_tdp_pte(_iter,                                                 \
> +               __va((_private) ? _mmu->private_root_hpa : _mmu->root_hpa),     \
> +               _mmu->shadow_root_level, _start, _end)
>
>  /*
>   * Yield if the MMU lock is contended or this thread needs to return control
> @@ -731,6 +800,18 @@ static bool zap_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
>          */
>         end = min(end, max_gfn_host);
>
> +       /*
> +        * Extend [start, end) to include GFN shared bit when TDX is enabled,
> +        * and for shared mapping range.
> +        */
> +       if (is_private_sp(root)) {
> +               start = kvm_gfn_private(kvm, start);
> +               end = kvm_gfn_private(kvm, end);
> +       } else {
> +               start = kvm_gfn_shared(kvm, start);
> +               end = kvm_gfn_shared(kvm, end);
> +       }
> +
>         kvm_lockdep_assert_mmu_lock_held(kvm, shared);
>
>         rcu_read_lock();
> @@ -783,13 +864,18 @@ static bool zap_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
>   * MMU lock.
>   */
>  bool __kvm_tdp_mmu_zap_gfn_range(struct kvm *kvm, int as_id, gfn_t start,
> -                                gfn_t end, bool can_yield, bool flush)
> +                                gfn_t end, bool can_yield, bool flush,
> +                                bool zap_private)
>  {
>         struct kvm_mmu_page *root;
>
> -       for_each_tdp_mmu_root_yield_safe(kvm, root, as_id, false)
> +       for_each_tdp_mmu_root_yield_safe(kvm, root, as_id, false) {
> +               /* Skip private page table if not requested */
> +               if (!zap_private && is_private_sp(root))
> +                       continue;
>                 flush = zap_gfn_range(kvm, root, start, end, can_yield, flush,
>                                       false);
> +       }
>
>         return flush;
>  }
> @@ -800,7 +886,7 @@ void kvm_tdp_mmu_zap_all(struct kvm *kvm)
>         int i;
>
>         for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
> -               flush = kvm_tdp_mmu_zap_gfn_range(kvm, i, 0, -1ull, flush);
> +               flush = kvm_tdp_mmu_zap_gfn_range(kvm, i, 0, -1ull, flush, true);
>
>         if (flush)
>                 kvm_flush_remote_tlbs(kvm);
> @@ -851,6 +937,13 @@ void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm)
>         while (root) {
>                 next_root = next_invalidated_root(kvm, root);
>
> +               /*
> +                * Private table is only torn down when VM is destroyed.
> +                * It is a bug to zap private table here.
> +                */
> +               if (WARN_ON(is_private_sp(root)))
> +                       goto out;
> +
>                 rcu_read_unlock();
>
>                 flush = zap_gfn_range(kvm, root, 0, -1ull, true, flush, true);
> @@ -865,7 +958,7 @@ void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm)
>
>                 rcu_read_lock();
>         }
> -
> +out:
>         rcu_read_unlock();
>
>         if (flush)
> @@ -897,9 +990,16 @@ void kvm_tdp_mmu_invalidate_all_roots(struct kvm *kvm)
>         struct kvm_mmu_page *root;
>
>         lockdep_assert_held_write(&kvm->mmu_lock);
> -       list_for_each_entry(root, &kvm->arch.tdp_mmu_roots, link)
> +       list_for_each_entry(root, &kvm->arch.tdp_mmu_roots, link) {
> +               /*
> +                * Skip private root since private page table
> +                * is only torn down when VM is destroyed.
> +                */
> +               if (is_private_sp(root))
> +                       continue;
>                 if (refcount_inc_not_zero(&root->tdp_mmu_root_count))
>                         root->role.invalid = true;
> +       }
>  }
>
>  /*
> @@ -914,14 +1014,23 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu,
>         u64 new_spte;
>         int ret = RET_PF_FIXED;
>         bool wrprot = false;
> +       unsigned long pte_access = ACC_ALL;
>
>         WARN_ON(sp->role.level != fault->goal_level);
> +
> +       /* TDX shared GPAs are no executable, enforce this for the SDV. */
> +       if (!kvm_is_private_gfn(vcpu->kvm, iter->gfn))
> +               pte_access &= ~ACC_EXEC_MASK;
> +
>         if (unlikely(!fault->slot))
> -               new_spte = make_mmio_spte(vcpu, iter->gfn, ACC_ALL);
> +               new_spte = make_mmio_spte(vcpu,
> +                               tdp_iter_gfn_unalias(vcpu->kvm, iter),
> +                               pte_access);
>         else
> -               wrprot = make_spte(vcpu, sp, fault->slot, ACC_ALL, iter->gfn,
> -                                        fault->pfn, iter->old_spte, fault->prefetch, true,
> -                                        fault->map_writable, &new_spte);
> +               wrprot = make_spte(vcpu, sp, fault->slot, pte_access,
> +                               tdp_iter_gfn_unalias(vcpu->kvm, iter),
> +                               fault->pfn, iter->old_spte, fault->prefetch,
> +                               true, fault->map_writable, &new_spte);
>
>         if (new_spte == iter->old_spte)
>                 ret = RET_PF_SPURIOUS;
> @@ -959,7 +1068,8 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu,
>  }
>
>  static bool tdp_mmu_populate_nonleaf(
> -       struct kvm_vcpu *vcpu, struct tdp_iter *iter, bool account_nx)
> +       struct kvm_vcpu *vcpu, struct tdp_iter *iter, bool is_private,
> +       bool account_nx)
>  {
>         struct kvm_mmu_page *sp;
>         u64 *child_pt;
> @@ -968,7 +1078,7 @@ static bool tdp_mmu_populate_nonleaf(
>         WARN_ON(is_shadow_present_pte(iter->old_spte));
>         WARN_ON(is_removed_spte(iter->old_spte));
>
> -       sp = alloc_tdp_mmu_page(vcpu, iter->gfn, iter->level - 1);
> +       sp = alloc_tdp_mmu_page(vcpu, iter->gfn, iter->level - 1, is_private);
>         child_pt = sp->spt;
>
>         new_spte = make_nonleaf_spte(child_pt, !shadow_accessed_mask);
> @@ -991,6 +1101,8 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
>  {
>         struct kvm_mmu *mmu = vcpu->arch.mmu;
>         struct tdp_iter iter;
> +       gfn_t raw_gfn;
> +       bool is_private;
>         int ret;
>
>         kvm_mmu_hugepage_adjust(vcpu, fault);
> @@ -999,7 +1111,17 @@ 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);
> +       is_private = kvm_is_private_gfn(vcpu->kvm, raw_gfn);
> +
> +       if (is_error_noslot_pfn(fault->pfn) || kvm_is_reserved_pfn(fault->pfn)) {
> +               if (is_private) {
> +                       rcu_read_unlock();
> +                       return -EFAULT;
> +               }
> +       }
> +
> +       tdp_mmu_for_each_pte(iter, mmu, is_private, raw_gfn, raw_gfn + 1) {
>                 if (fault->nx_huge_page_workaround_enabled)
>                         disallowed_hugepage_adjust(fault, iter.old_spte, iter.level);
>
> @@ -1015,6 +1137,12 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
>                     is_large_pte(iter.old_spte)) {
>                         if (!tdp_mmu_zap_spte_atomic(vcpu->kvm, &iter))
>                                 break;
> +                       /*
> +                        * TODO: large page support.
> +                        * Doesn't support large page for TDX now
> +                        */
> +                       WARN_ON(is_private_spte(&iter.old_spte));

The above line is causing a null ptr dereferencing when running the
KVM unit tests.
It should be is_private_spte(iter.sptep) instead of
is_private_spte(&iter.old_spte)
While old_spte holds a snapshot of the value pointed to by sptep,
&old_spte is not equivalent to sptep.

>
> +
>
>
>                         /*
>                          * The iter must explicitly re-read the spte here
> @@ -1037,7 +1165,8 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
>
>                         account_nx = fault->huge_page_disallowed &&
>                                 fault->req_level >= iter.level;
> -                       if (!tdp_mmu_populate_nonleaf(vcpu, &iter, account_nx))
> +                       if (!tdp_mmu_populate_nonleaf(
> +                                       vcpu, &iter, is_private, account_nx))
>                                 break;
>                 }
>         }
> @@ -1058,9 +1187,12 @@ bool kvm_tdp_mmu_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range,
>  {
>         struct kvm_mmu_page *root;
>
> -       for_each_tdp_mmu_root_yield_safe(kvm, root, range->slot->as_id, false)
> +       for_each_tdp_mmu_root_yield_safe(kvm, root, range->slot->as_id, false) {
> +               if (is_private_sp(root))
> +                       continue;
>                 flush = zap_gfn_range(kvm, root, range->start, range->end,
> -                                     range->may_block, flush, false);
> +                               range->may_block, flush, false);
> +       }
>
>         return flush;
>  }
> @@ -1513,10 +1645,14 @@ int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes,
>         struct kvm_mmu *mmu = vcpu->arch.mmu;
>         gfn_t gfn = addr >> PAGE_SHIFT;
>         int leaf = -1;
> +       bool is_private = kvm_is_private_gfn(vcpu->kvm, gfn);
>
>         *root_level = vcpu->arch.mmu->shadow_root_level;
>
> -       tdp_mmu_for_each_pte(iter, mmu, gfn, gfn + 1) {
> +       if (WARN_ON(is_private))
> +               return leaf;
> +
> +       tdp_mmu_for_each_pte(iter, mmu, false, gfn, gfn + 1) {
>                 leaf = iter.level;
>                 sptes[leaf] = iter.old_spte;
>         }
> @@ -1542,12 +1678,16 @@ u64 *kvm_tdp_mmu_fast_pf_get_last_sptep(struct kvm_vcpu *vcpu, u64 addr,
>         struct kvm_mmu *mmu = vcpu->arch.mmu;
>         gfn_t gfn = addr >> PAGE_SHIFT;
>         tdp_ptep_t sptep = NULL;
> +       bool is_private = kvm_is_private_gfn(vcpu->kvm, gfn);
>
> -       tdp_mmu_for_each_pte(iter, mmu, gfn, gfn + 1) {
> +       if (is_private)
> +               goto out;
> +
> +       tdp_mmu_for_each_pte(iter, mmu, false, gfn, gfn + 1) {
>                 *spte = iter.old_spte;
>                 sptep = iter.sptep;
>         }
> -
> +out:
>         /*
>          * Perform the rcu_dereference to get the raw spte pointer value since
>          * we are passing it up to fast_page_fault, which is shared with the
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h
> index 3899004a5d91..7c62f694a465 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.h
> +++ b/arch/x86/kvm/mmu/tdp_mmu.h
> @@ -5,7 +5,7 @@
>
>  #include <linux/kvm_host.h>
>
> -hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu);
> +hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu, bool private);
>
>  __must_check static inline bool kvm_tdp_mmu_get_root(struct kvm *kvm,
>                                                      struct kvm_mmu_page *root)
> @@ -20,11 +20,14 @@ void kvm_tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root,
>                           bool shared);
>
>  bool __kvm_tdp_mmu_zap_gfn_range(struct kvm *kvm, int as_id, gfn_t start,
> -                                gfn_t end, bool can_yield, bool flush);
> +                                gfn_t end, bool can_yield, bool flush,
> +                                bool zap_private);
>  static inline bool kvm_tdp_mmu_zap_gfn_range(struct kvm *kvm, int as_id,
> -                                            gfn_t start, gfn_t end, bool flush)
> +                                            gfn_t start, gfn_t end, bool flush,
> +                                            bool zap_private)
>  {
> -       return __kvm_tdp_mmu_zap_gfn_range(kvm, as_id, start, end, true, flush);
> +       return __kvm_tdp_mmu_zap_gfn_range(kvm, as_id, start, end, true, flush,
> +                       zap_private);
>  }
>  static inline bool kvm_tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
>  {
> @@ -41,7 +44,7 @@ static inline bool kvm_tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
>          */
>         lockdep_assert_held_write(&kvm->mmu_lock);
>         return __kvm_tdp_mmu_zap_gfn_range(kvm, kvm_mmu_page_as_id(sp),
> -                                          sp->gfn, end, false, false);
> +                                          sp->gfn, end, false, false, false);
>  }
>
>  void kvm_tdp_mmu_zap_all(struct kvm *kvm);
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index ae3bf553f215..d4e117f5b5b9 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -190,6 +190,7 @@ bool kvm_is_reserved_pfn(kvm_pfn_t pfn)
>
>         return true;
>  }
> +EXPORT_SYMBOL_GPL(kvm_is_reserved_pfn);
>
>  /*
>   * Switches to specified vcpu, until a matching vcpu_put()
> --
> 2.25.1
>

Sagi