KVM: x86: Add a helper to handle legal GPA with an alignment requirement

Add a helper to genericize checking for a legal GPA that also must
conform to an arbitrary alignment, and use it in the existing
page_address_valid().  Future patches will replace open coded variants
in VMX and SVM.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210204000117.3303214-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/cpuid.h

@@ -46,9 +46,15 @@ static inline bool kvm_vcpu_is_illegal_gpa(struct kvm_vcpu *vcpu, gpa_t gpa)
 	return !kvm_vcpu_is_legal_gpa(vcpu, gpa);
 }
 
+static inline bool kvm_vcpu_is_legal_aligned_gpa(struct kvm_vcpu *vcpu,
+						 gpa_t gpa, gpa_t alignment)
+{
+	return IS_ALIGNED(gpa, alignment) && kvm_vcpu_is_legal_gpa(vcpu, gpa);
+}
+
 static inline bool page_address_valid(struct kvm_vcpu *vcpu, gpa_t gpa)
 {
-	return PAGE_ALIGNED(gpa) && kvm_vcpu_is_legal_gpa(vcpu, gpa);
+	return kvm_vcpu_is_legal_aligned_gpa(vcpu, gpa, PAGE_SIZE);
 }
 
 struct cpuid_reg {