Re: [PATCH 1/4] KVM: delete .change_pte MMU notifier callback

[Anup Patel]

On Fri, Apr 5, 2024 at 5:28 PM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
> The .change_pte() MMU notifier callback was intended as an
> optimization. The original point of it was that KSM could tell KVM to flip
> its secondary PTE to a new location without having to first zap it. At
> the time there was also an .invalidate_page() callback; both of them were
> *not* bracketed by calls to mmu_notifier_invalidate_range_{start,end}(),
> and .invalidate_page() also doubled as a fallback implementation of
> .change_pte().
>
> Later on, however, both callbacks were changed to occur within an
> invalidate_range_start/end() block.
>
> In the case of .change_pte(), commit 6bdb913f0a70 ("mm: wrap calls to
> set_pte_at_notify with invalidate_range_start and invalidate_range_end",
> 2012-10-09) did so to remove the fallback from .invalidate_page() to
> .change_pte() and allow sleepable .invalidate_page() hooks.
>
> This however made KVM's usage of the .change_pte() callback completely
> moot, because KVM unmaps the sPTEs during .invalidate_range_start()
> and therefore .change_pte() has no hope of finding a sPTE to change.
> Drop the generic KVM code that dispatches to kvm_set_spte_gfn(), as
> well as all the architecture specific implementations.
>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>

For KVM RISC-V:
Acked-by: Anup Patel <anup@xxxxxxxxxxxxxx>

Regards,
Anup

> ---
>  arch/arm64/kvm/mmu.c                  | 34 -----------------
>  arch/loongarch/include/asm/kvm_host.h |  1 -
>  arch/loongarch/kvm/mmu.c              | 32 ----------------
>  arch/mips/kvm/mmu.c                   | 30 ---------------
>  arch/powerpc/include/asm/kvm_ppc.h    |  1 -
>  arch/powerpc/kvm/book3s.c             |  5 ---
>  arch/powerpc/kvm/book3s.h             |  1 -
>  arch/powerpc/kvm/book3s_64_mmu_hv.c   | 12 ------
>  arch/powerpc/kvm/book3s_hv.c          |  1 -
>  arch/powerpc/kvm/book3s_pr.c          |  7 ----
>  arch/powerpc/kvm/e500_mmu_host.c      |  6 ---
>  arch/riscv/kvm/mmu.c                  | 20 ----------
>  arch/x86/kvm/mmu/mmu.c                | 54 +--------------------------
>  arch/x86/kvm/mmu/spte.c               | 16 --------
>  arch/x86/kvm/mmu/spte.h               |  2 -
>  arch/x86/kvm/mmu/tdp_mmu.c            | 46 -----------------------
>  arch/x86/kvm/mmu/tdp_mmu.h            |  1 -
>  include/linux/kvm_host.h              |  2 -
>  include/trace/events/kvm.h            | 15 --------
>  virt/kvm/kvm_main.c                   | 43 ---------------------
>  20 files changed, 2 insertions(+), 327 deletions(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index dc04bc767865..ff17849be9f4 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1768,40 +1768,6 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
>         return false;
>  }
>
> -bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
> -{
> -       kvm_pfn_t pfn = pte_pfn(range->arg.pte);
> -
> -       if (!kvm->arch.mmu.pgt)
> -               return false;
> -
> -       WARN_ON(range->end - range->start != 1);
> -
> -       /*
> -        * If the page isn't tagged, defer to user_mem_abort() for sanitising
> -        * the MTE tags. The S2 pte should have been unmapped by
> -        * mmu_notifier_invalidate_range_end().
> -        */
> -       if (kvm_has_mte(kvm) && !page_mte_tagged(pfn_to_page(pfn)))
> -               return false;
> -
> -       /*
> -        * We've moved a page around, probably through CoW, so let's treat
> -        * it just like a translation fault and the map handler will clean
> -        * the cache to the PoC.
> -        *
> -        * The MMU notifiers will have unmapped a huge PMD before calling
> -        * ->change_pte() (which in turn calls kvm_set_spte_gfn()) and
> -        * therefore we never need to clear out a huge PMD through this
> -        * calling path and a memcache is not required.
> -        */
> -       kvm_pgtable_stage2_map(kvm->arch.mmu.pgt, range->start << PAGE_SHIFT,
> -                              PAGE_SIZE, __pfn_to_phys(pfn),
> -                              KVM_PGTABLE_PROT_R, NULL, 0);
> -
> -       return false;
> -}
> -
>  bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
>  {
>         u64 size = (range->end - range->start) << PAGE_SHIFT;
> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
> index 2d62f7b0d377..69305441f40d 100644
> --- a/arch/loongarch/include/asm/kvm_host.h
> +++ b/arch/loongarch/include/asm/kvm_host.h
> @@ -203,7 +203,6 @@ void kvm_flush_tlb_all(void);
>  void kvm_flush_tlb_gpa(struct kvm_vcpu *vcpu, unsigned long gpa);
>  int kvm_handle_mm_fault(struct kvm_vcpu *vcpu, unsigned long badv, bool write);
>
> -void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);
>  int kvm_unmap_hva_range(struct kvm *kvm, unsigned long start, unsigned long end, bool blockable);
>  int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end);
>  int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
> diff --git a/arch/loongarch/kvm/mmu.c b/arch/loongarch/kvm/mmu.c
> index a556cff35740..98883aa23ab8 100644
> --- a/arch/loongarch/kvm/mmu.c
> +++ b/arch/loongarch/kvm/mmu.c
> @@ -494,38 +494,6 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
>                         range->end << PAGE_SHIFT, &ctx);
>  }
>
> -bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
> -{
> -       unsigned long prot_bits;
> -       kvm_pte_t *ptep;
> -       kvm_pfn_t pfn = pte_pfn(range->arg.pte);
> -       gpa_t gpa = range->start << PAGE_SHIFT;
> -
> -       ptep = kvm_populate_gpa(kvm, NULL, gpa, 0);
> -       if (!ptep)
> -               return false;
> -
> -       /* Replacing an absent or old page doesn't need flushes */
> -       if (!kvm_pte_present(NULL, ptep) || !kvm_pte_young(*ptep)) {
> -               kvm_set_pte(ptep, 0);
> -               return false;
> -       }
> -
> -       /* Fill new pte if write protected or page migrated */
> -       prot_bits = _PAGE_PRESENT | __READABLE;
> -       prot_bits |= _CACHE_MASK & pte_val(range->arg.pte);
> -
> -       /*
> -        * Set _PAGE_WRITE or _PAGE_DIRTY iff old and new pte both support
> -        * _PAGE_WRITE for map_page_fast if next page write fault
> -        * _PAGE_DIRTY since gpa has already recorded as dirty page
> -        */
> -       prot_bits |= __WRITEABLE & *ptep & pte_val(range->arg.pte);
> -       kvm_set_pte(ptep, kvm_pfn_pte(pfn, __pgprot(prot_bits)));
> -
> -       return true;
> -}
> -
>  bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
>  {
>         kvm_ptw_ctx ctx;
> diff --git a/arch/mips/kvm/mmu.c b/arch/mips/kvm/mmu.c
> index 467ee6b95ae1..c17157e700c0 100644
> --- a/arch/mips/kvm/mmu.c
> +++ b/arch/mips/kvm/mmu.c
> @@ -444,36 +444,6 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
>         return true;
>  }
>
> -bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
> -{
> -       gpa_t gpa = range->start << PAGE_SHIFT;
> -       pte_t hva_pte = range->arg.pte;
> -       pte_t *gpa_pte = kvm_mips_pte_for_gpa(kvm, NULL, gpa);
> -       pte_t old_pte;
> -
> -       if (!gpa_pte)
> -               return false;
> -
> -       /* Mapping may need adjusting depending on memslot flags */
> -       old_pte = *gpa_pte;
> -       if (range->slot->flags & KVM_MEM_LOG_DIRTY_PAGES && !pte_dirty(old_pte))
> -               hva_pte = pte_mkclean(hva_pte);
> -       else if (range->slot->flags & KVM_MEM_READONLY)
> -               hva_pte = pte_wrprotect(hva_pte);
> -
> -       set_pte(gpa_pte, hva_pte);
> -
> -       /* Replacing an absent or old page doesn't need flushes */
> -       if (!pte_present(old_pte) || !pte_young(old_pte))
> -               return false;
> -
> -       /* Pages swapped, aged, moved, or cleaned require flushes */
> -       return !pte_present(hva_pte) ||
> -              !pte_young(hva_pte) ||
> -              pte_pfn(old_pte) != pte_pfn(hva_pte) ||
> -              (pte_dirty(old_pte) && !pte_dirty(hva_pte));
> -}
> -
>  bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
>  {
>         return kvm_mips_mkold_gpa_pt(kvm, range->start, range->end);
> diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
> index 3281215097cc..ca3829d47ab7 100644
> --- a/arch/powerpc/include/asm/kvm_ppc.h
> +++ b/arch/powerpc/include/asm/kvm_ppc.h
> @@ -287,7 +287,6 @@ struct kvmppc_ops {
>         bool (*unmap_gfn_range)(struct kvm *kvm, struct kvm_gfn_range *range);
>         bool (*age_gfn)(struct kvm *kvm, struct kvm_gfn_range *range);
>         bool (*test_age_gfn)(struct kvm *kvm, struct kvm_gfn_range *range);
> -       bool (*set_spte_gfn)(struct kvm *kvm, struct kvm_gfn_range *range);
>         void (*free_memslot)(struct kvm_memory_slot *slot);
>         int (*init_vm)(struct kvm *kvm);
>         void (*destroy_vm)(struct kvm *kvm);
> diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
> index 8acec144120e..0d0624088e6b 100644
> --- a/arch/powerpc/kvm/book3s.c
> +++ b/arch/powerpc/kvm/book3s.c
> @@ -899,11 +899,6 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
>         return kvm->arch.kvm_ops->test_age_gfn(kvm, range);
>  }
>
> -bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
> -{
> -       return kvm->arch.kvm_ops->set_spte_gfn(kvm, range);
> -}
> -
>  int kvmppc_core_init_vm(struct kvm *kvm)
>  {
>
> diff --git a/arch/powerpc/kvm/book3s.h b/arch/powerpc/kvm/book3s.h
> index 58391b4b32ed..4aa2ab89afbc 100644
> --- a/arch/powerpc/kvm/book3s.h
> +++ b/arch/powerpc/kvm/book3s.h
> @@ -12,7 +12,6 @@ extern void kvmppc_core_flush_memslot_hv(struct kvm *kvm,
>  extern bool kvm_unmap_gfn_range_hv(struct kvm *kvm, struct kvm_gfn_range *range);
>  extern bool kvm_age_gfn_hv(struct kvm *kvm, struct kvm_gfn_range *range);
>  extern bool kvm_test_age_gfn_hv(struct kvm *kvm, struct kvm_gfn_range *range);
> -extern bool kvm_set_spte_gfn_hv(struct kvm *kvm, struct kvm_gfn_range *range);
>
>  extern int kvmppc_mmu_init_pr(struct kvm_vcpu *vcpu);
>  extern void kvmppc_mmu_destroy_pr(struct kvm_vcpu *vcpu);
> diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> index 2b1f0cdd8c18..1b51b1c4713b 100644
> --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
> +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> @@ -1010,18 +1010,6 @@ bool kvm_test_age_gfn_hv(struct kvm *kvm, struct kvm_gfn_range *range)
>                 return kvm_test_age_rmapp(kvm, range->slot, range->start);
>  }
>
> -bool kvm_set_spte_gfn_hv(struct kvm *kvm, struct kvm_gfn_range *range)
> -{
> -       WARN_ON(range->start + 1 != range->end);
> -
> -       if (kvm_is_radix(kvm))
> -               kvm_unmap_radix(kvm, range->slot, range->start);
> -       else
> -               kvm_unmap_rmapp(kvm, range->slot, range->start);
> -
> -       return false;
> -}
> -
>  static int vcpus_running(struct kvm *kvm)
>  {
>         return atomic_read(&kvm->arch.vcpus_running) != 0;
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 8e86eb577eb8..35cb014a0c51 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -6364,7 +6364,6 @@ static struct kvmppc_ops kvm_ops_hv = {
>         .unmap_gfn_range = kvm_unmap_gfn_range_hv,
>         .age_gfn = kvm_age_gfn_hv,
>         .test_age_gfn = kvm_test_age_gfn_hv,
> -       .set_spte_gfn = kvm_set_spte_gfn_hv,
>         .free_memslot = kvmppc_core_free_memslot_hv,
>         .init_vm =  kvmppc_core_init_vm_hv,
>         .destroy_vm = kvmppc_core_destroy_vm_hv,
> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
> index 5b92619a05fd..a7d7137ea0c8 100644
> --- a/arch/powerpc/kvm/book3s_pr.c
> +++ b/arch/powerpc/kvm/book3s_pr.c
> @@ -461,12 +461,6 @@ static bool kvm_test_age_gfn_pr(struct kvm *kvm, struct kvm_gfn_range *range)
>         return false;
>  }
>
> -static bool kvm_set_spte_gfn_pr(struct kvm *kvm, struct kvm_gfn_range *range)
> -{
> -       /* The page will get remapped properly on its next fault */
> -       return do_kvm_unmap_gfn(kvm, range);
> -}
> -
>  /*****************************************/
>
>  static void kvmppc_set_msr_pr(struct kvm_vcpu *vcpu, u64 msr)
> @@ -2071,7 +2065,6 @@ static struct kvmppc_ops kvm_ops_pr = {
>         .unmap_gfn_range = kvm_unmap_gfn_range_pr,
>         .age_gfn  = kvm_age_gfn_pr,
>         .test_age_gfn = kvm_test_age_gfn_pr,
> -       .set_spte_gfn = kvm_set_spte_gfn_pr,
>         .free_memslot = kvmppc_core_free_memslot_pr,
>         .init_vm = kvmppc_core_init_vm_pr,
>         .destroy_vm = kvmppc_core_destroy_vm_pr,
> diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_host.c
> index ccb8f16ffe41..c664fdec75b1 100644
> --- a/arch/powerpc/kvm/e500_mmu_host.c
> +++ b/arch/powerpc/kvm/e500_mmu_host.c
> @@ -747,12 +747,6 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
>         return false;
>  }
>
> -bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
> -{
> -       /* The page will get remapped properly on its next fault */
> -       return kvm_e500_mmu_unmap_gfn(kvm, range);
> -}
> -
>  /*****************************************/
>
>  int e500_mmu_host_init(struct kvmppc_vcpu_e500 *vcpu_e500)
> diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
> index a9e2fd7245e1..b63650f9b966 100644
> --- a/arch/riscv/kvm/mmu.c
> +++ b/arch/riscv/kvm/mmu.c
> @@ -550,26 +550,6 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
>         return false;
>  }
>
> -bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
> -{
> -       int ret;
> -       kvm_pfn_t pfn = pte_pfn(range->arg.pte);
> -
> -       if (!kvm->arch.pgd)
> -               return false;
> -
> -       WARN_ON(range->end - range->start != 1);
> -
> -       ret = gstage_map_page(kvm, NULL, range->start << PAGE_SHIFT,
> -                             __pfn_to_phys(pfn), PAGE_SIZE, true, true);
> -       if (ret) {
> -               kvm_debug("Failed to map G-stage page (error %d)\n", ret);
> -               return true;
> -       }
> -
> -       return false;
> -}
> -
>  bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
>  {
>         pte_t *ptep;
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 0049d49aa913..87ba2a9da196 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -432,8 +432,8 @@ static u64 __update_clear_spte_slow(u64 *sptep, u64 spte)
>   * The idea using the light way get the spte on x86_32 guest is from
>   * gup_get_pte (mm/gup.c).
>   *
> - * An spte tlb flush may be pending, because kvm_set_pte_rmap
> - * coalesces them and we are running out of the MMU lock.  Therefore
> + * An spte tlb flush may be pending, because they are coalesced and
> + * we are running out of the MMU lock.  Therefore
>   * we need to protect against in-progress updates of the spte.
>   *
>   * Reading the spte while an update is in progress may get the old value
> @@ -1454,43 +1454,6 @@ static bool kvm_zap_rmap(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
>         return __kvm_zap_rmap(kvm, rmap_head, slot);
>  }
>
> -static bool kvm_set_pte_rmap(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
> -                            struct kvm_memory_slot *slot, gfn_t gfn, int level,
> -                            pte_t pte)
> -{
> -       u64 *sptep;
> -       struct rmap_iterator iter;
> -       bool need_flush = false;
> -       u64 new_spte;
> -       kvm_pfn_t new_pfn;
> -
> -       WARN_ON_ONCE(pte_huge(pte));
> -       new_pfn = pte_pfn(pte);
> -
> -restart:
> -       for_each_rmap_spte(rmap_head, &iter, sptep) {
> -               need_flush = true;
> -
> -               if (pte_write(pte)) {
> -                       kvm_zap_one_rmap_spte(kvm, rmap_head, sptep);
> -                       goto restart;
> -               } else {
> -                       new_spte = kvm_mmu_changed_pte_notifier_make_spte(
> -                                       *sptep, new_pfn);
> -
> -                       mmu_spte_clear_track_bits(kvm, sptep);
> -                       mmu_spte_set(sptep, new_spte);
> -               }
> -       }
> -
> -       if (need_flush && kvm_available_flush_remote_tlbs_range()) {
> -               kvm_flush_remote_tlbs_gfn(kvm, gfn, level);
> -               return false;
> -       }
> -
> -       return need_flush;
> -}
> -
>  struct slot_rmap_walk_iterator {
>         /* input fields. */
>         const struct kvm_memory_slot *slot;
> @@ -1596,19 +1559,6 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
>         return flush;
>  }
>
> -bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
> -{
> -       bool flush = false;
> -
> -       if (kvm_memslots_have_rmaps(kvm))
> -               flush = kvm_handle_gfn_range(kvm, range, kvm_set_pte_rmap);
> -
> -       if (tdp_mmu_enabled)
> -               flush |= kvm_tdp_mmu_set_spte_gfn(kvm, range);
> -
> -       return flush;
> -}
> -
>  static bool kvm_age_rmap(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
>                          struct kvm_memory_slot *slot, gfn_t gfn, int level,
>                          pte_t unused)
> diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c
> index 318135daf685..283af5b90016 100644
> --- a/arch/x86/kvm/mmu/spte.c
> +++ b/arch/x86/kvm/mmu/spte.c
> @@ -322,22 +322,6 @@ u64 make_nonleaf_spte(u64 *child_pt, bool ad_disabled)
>         return spte;
>  }
>
> -u64 kvm_mmu_changed_pte_notifier_make_spte(u64 old_spte, kvm_pfn_t new_pfn)
> -{
> -       u64 new_spte;
> -
> -       new_spte = old_spte & ~SPTE_BASE_ADDR_MASK;
> -       new_spte |= (u64)new_pfn << PAGE_SHIFT;
> -
> -       new_spte &= ~PT_WRITABLE_MASK;
> -       new_spte &= ~shadow_host_writable_mask;
> -       new_spte &= ~shadow_mmu_writable_mask;
> -
> -       new_spte = mark_spte_for_access_track(new_spte);
> -
> -       return new_spte;
> -}
> -
>  u64 mark_spte_for_access_track(u64 spte)
>  {
>         if (spte_ad_enabled(spte))
> diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
> index 1a163aee9ec6..92da4c419171 100644
> --- a/arch/x86/kvm/mmu/spte.h
> +++ b/arch/x86/kvm/mmu/spte.h
> @@ -511,8 +511,6 @@ static inline u64 restore_acc_track_spte(u64 spte)
>         return spte;
>  }
>
> -u64 kvm_mmu_changed_pte_notifier_make_spte(u64 old_spte, kvm_pfn_t new_pfn);
> -
>  void __init kvm_mmu_spte_module_init(void);
>  void kvm_mmu_reset_all_pte_masks(void);
>
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index 3627744fcab6..fbb86932b766 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -1250,52 +1250,6 @@ bool kvm_tdp_mmu_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
>         return kvm_tdp_mmu_handle_gfn(kvm, range, test_age_gfn);
>  }
>
> -static bool set_spte_gfn(struct kvm *kvm, struct tdp_iter *iter,
> -                        struct kvm_gfn_range *range)
> -{
> -       u64 new_spte;
> -
> -       /* Huge pages aren't expected to be modified without first being zapped. */
> -       WARN_ON_ONCE(pte_huge(range->arg.pte) || range->start + 1 != range->end);
> -
> -       if (iter->level != PG_LEVEL_4K ||
> -           !is_shadow_present_pte(iter->old_spte))
> -               return false;
> -
> -       /*
> -        * Note, when changing a read-only SPTE, it's not strictly necessary to
> -        * zero the SPTE before setting the new PFN, but doing so preserves the
> -        * invariant that the PFN of a present * leaf SPTE can never change.
> -        * See handle_changed_spte().
> -        */
> -       tdp_mmu_iter_set_spte(kvm, iter, SHADOW_NONPRESENT_VALUE);
> -
> -       if (!pte_write(range->arg.pte)) {
> -               new_spte = kvm_mmu_changed_pte_notifier_make_spte(iter->old_spte,
> -                                                                 pte_pfn(range->arg.pte));
> -
> -               tdp_mmu_iter_set_spte(kvm, iter, new_spte);
> -       }
> -
> -       return true;
> -}
> -
> -/*
> - * Handle the changed_pte MMU notifier for the TDP MMU.
> - * data is a pointer to the new pte_t mapping the HVA specified by the MMU
> - * notifier.
> - * Returns non-zero if a flush is needed before releasing the MMU lock.
> - */
> -bool kvm_tdp_mmu_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
> -{
> -       /*
> -        * No need to handle the remote TLB flush under RCU protection, the
> -        * target SPTE _must_ be a leaf SPTE, i.e. cannot result in freeing a
> -        * shadow page. See the WARN on pfn_changed in handle_changed_spte().
> -        */
> -       return kvm_tdp_mmu_handle_gfn(kvm, range, set_spte_gfn);
> -}
> -
>  /*
>   * Remove write access from all SPTEs at or above min_level that map GFNs
>   * [start, end). Returns true if an SPTE has been changed and the TLBs need to
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h
> index 6e1ea04ca885..58b55e61bd33 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.h
> +++ b/arch/x86/kvm/mmu/tdp_mmu.h
> @@ -31,7 +31,6 @@ bool kvm_tdp_mmu_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range,
>                                  bool flush);
>  bool kvm_tdp_mmu_age_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range);
>  bool kvm_tdp_mmu_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range);
> -bool kvm_tdp_mmu_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range);
>
>  bool kvm_tdp_mmu_wrprot_slot(struct kvm *kvm,
>                              const struct kvm_memory_slot *slot, int min_level);
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index ab439706ea2f..8dea11701ab2 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -259,7 +259,6 @@ int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu);
>
>  #ifdef CONFIG_KVM_GENERIC_MMU_NOTIFIER
>  union kvm_mmu_notifier_arg {
> -       pte_t pte;
>         unsigned long attributes;
>  };
>
> @@ -273,7 +272,6 @@ struct kvm_gfn_range {
>  bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range);
>  bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range);
>  bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range);
> -bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range);
>  #endif
>
>  enum {
> diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
> index 011fba6b5552..74e40d5d4af4 100644
> --- a/include/trace/events/kvm.h
> +++ b/include/trace/events/kvm.h
> @@ -456,21 +456,6 @@ TRACE_EVENT(kvm_unmap_hva_range,
>                   __entry->start, __entry->end)
>  );
>
> -TRACE_EVENT(kvm_set_spte_hva,
> -       TP_PROTO(unsigned long hva),
> -       TP_ARGS(hva),
> -
> -       TP_STRUCT__entry(
> -               __field(        unsigned long,  hva             )
> -       ),
> -
> -       TP_fast_assign(
> -               __entry->hva            = hva;
> -       ),
> -
> -       TP_printk("mmu notifier set pte hva: %#016lx", __entry->hva)
> -);
> -
>  TRACE_EVENT(kvm_age_hva,
>         TP_PROTO(unsigned long start, unsigned long end),
>         TP_ARGS(start, end),
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 4eb8afd0b961..2fcd9979752a 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -717,48 +717,6 @@ static __always_inline int kvm_handle_hva_range_no_flush(struct mmu_notifier *mn
>         return __kvm_handle_hva_range(kvm, &range).ret;
>  }
>
> -static bool kvm_change_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
> -{
> -       /*
> -        * Skipping invalid memslots is correct if and only change_pte() is
> -        * surrounded by invalidate_range_{start,end}(), which is currently
> -        * guaranteed by the primary MMU.  If that ever changes, KVM needs to
> -        * unmap the memslot instead of skipping the memslot to ensure that KVM
> -        * doesn't hold references to the old PFN.
> -        */
> -       WARN_ON_ONCE(!READ_ONCE(kvm->mn_active_invalidate_count));
> -
> -       if (range->slot->flags & KVM_MEMSLOT_INVALID)
> -               return false;
> -
> -       return kvm_set_spte_gfn(kvm, range);
> -}
> -
> -static void kvm_mmu_notifier_change_pte(struct mmu_notifier *mn,
> -                                       struct mm_struct *mm,
> -                                       unsigned long address,
> -                                       pte_t pte)
> -{
> -       struct kvm *kvm = mmu_notifier_to_kvm(mn);
> -       const union kvm_mmu_notifier_arg arg = { .pte = pte };
> -
> -       trace_kvm_set_spte_hva(address);
> -
> -       /*
> -        * .change_pte() must be surrounded by .invalidate_range_{start,end}().
> -        * If mmu_invalidate_in_progress is zero, then no in-progress
> -        * invalidations, including this one, found a relevant memslot at
> -        * start(); rechecking memslots here is unnecessary.  Note, a false
> -        * positive (count elevated by a different invalidation) is sub-optimal
> -        * but functionally ok.
> -        */
> -       WARN_ON_ONCE(!READ_ONCE(kvm->mn_active_invalidate_count));
> -       if (!READ_ONCE(kvm->mmu_invalidate_in_progress))
> -               return;
> -
> -       kvm_handle_hva_range(mn, address, address + 1, arg, kvm_change_spte_gfn);
> -}
> -
>  void kvm_mmu_invalidate_begin(struct kvm *kvm)
>  {
>         lockdep_assert_held_write(&kvm->mmu_lock);
> @@ -976,7 +934,6 @@ static const struct mmu_notifier_ops kvm_mmu_notifier_ops = {
>         .clear_flush_young      = kvm_mmu_notifier_clear_flush_young,
>         .clear_young            = kvm_mmu_notifier_clear_young,
>         .test_young             = kvm_mmu_notifier_test_young,
> -       .change_pte             = kvm_mmu_notifier_change_pte,
>         .release                = kvm_mmu_notifier_release,
>  };
>
> --
> 2.43.0
>
>