KVM: Remove kvm_vcpu_gfn_to_page() and kvm_vcpu_gpa_to_page()

Drop helpers to convert a gfn/gpa to a 'struct page' in the context of a
vCPU.  KVM doesn't require that guests be backed by 'struct page' memory,
thus any use of helpers that assume 'struct page' is bound to be flawed,
as was the case for the recently removed last user in x86's nested VMX.

No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220429010416.2788472-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/linux/kvm_host.h

@@ -1230,7 +1230,6 @@ struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn
 kvm_pfn_t kvm_vcpu_gfn_to_pfn_atomic(struct kvm_vcpu *vcpu, gfn_t gfn);
 kvm_pfn_t kvm_vcpu_gfn_to_pfn(struct kvm_vcpu *vcpu, gfn_t gfn);
 int kvm_vcpu_map(struct kvm_vcpu *vcpu, gpa_t gpa, struct kvm_host_map *map);
-struct page *kvm_vcpu_gfn_to_page(struct kvm_vcpu *vcpu, gfn_t gfn);
 void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map, bool dirty);
 unsigned long kvm_vcpu_gfn_to_hva(struct kvm_vcpu *vcpu, gfn_t gfn);
 unsigned long kvm_vcpu_gfn_to_hva_prot(struct kvm_vcpu *vcpu, gfn_t gfn, bool *writable);
@@ -1718,12 +1717,6 @@ static inline hpa_t pfn_to_hpa(kvm_pfn_t pfn)
 	return (hpa_t)pfn << PAGE_SHIFT;
 }
 
-static inline struct page *kvm_vcpu_gpa_to_page(struct kvm_vcpu *vcpu,
-						gpa_t gpa)
-{
-	return kvm_vcpu_gfn_to_page(vcpu, gpa_to_gfn(gpa));
-}
-
 static inline bool kvm_is_error_gpa(struct kvm *kvm, gpa_t gpa)
 {
 	unsigned long hva = gfn_to_hva(kvm, gpa_to_gfn(gpa));

virt/kvm/kvm_main.c

@@ -2720,8 +2720,18 @@ int gfn_to_page_many_atomic(struct kvm_memory_slot *slot, gfn_t gfn,
 }
 EXPORT_SYMBOL_GPL(gfn_to_page_many_atomic);
 
-static struct page *kvm_pfn_to_page(kvm_pfn_t pfn)
+/*
+ * Do not use this helper unless you are absolutely certain the gfn _must_ be
+ * backed by 'struct page'.  A valid example is if the backing memslot is
+ * controlled by KVM.  Note, if the returned page is valid, it's refcount has
+ * been elevated by gfn_to_pfn().
+ */
+struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
 {
+	kvm_pfn_t pfn;
+
+	pfn = gfn_to_pfn(kvm, gfn);
+
 	if (is_error_noslot_pfn(pfn))
 		return KVM_ERR_PTR_BAD_PAGE;
 
@@ -2730,15 +2740,6 @@ static struct page *kvm_pfn_to_page(kvm_pfn_t pfn)
 
 	return pfn_to_page(pfn);
 }
-
-struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
-{
-	kvm_pfn_t pfn;
-
-	pfn = gfn_to_pfn(kvm, gfn);
-
-	return kvm_pfn_to_page(pfn);
-}
 EXPORT_SYMBOL_GPL(gfn_to_page);
 
 void kvm_release_pfn(kvm_pfn_t pfn, bool dirty)
@@ -2808,16 +2809,6 @@ void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map, bool dirty)
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_unmap);
 
-struct page *kvm_vcpu_gfn_to_page(struct kvm_vcpu *vcpu, gfn_t gfn)
-{
-	kvm_pfn_t pfn;
-
-	pfn = kvm_vcpu_gfn_to_pfn(vcpu, gfn);
-
-	return kvm_pfn_to_page(pfn);
-}
-EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_page);
-
 static bool kvm_is_ad_tracked_page(struct page *page)
 {
 	/*