KVM: delete .change_pte MMU notifier callback

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@redhat.com>
Acked-by: Anup Patel <anup@brainfault.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Message-ID: <20240405115815.3226315-2-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

7 files changed, 0 insertions, 33 deletions

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)