kvm: x86: mmu: Drop the need_remote_flush() function

This is only used by kvm_mmu_pte_write(), which no longer actually
creates the new SPTE and instead just clears the old SPTE. So we
just need to check if the old SPTE was shadow-present instead of
calling need_remote_flush(). Hence we can drop this function. It was
incomplete anyway as it didn't take access-tracking into account.

This patch should not result in any functional change.

Signed-off-by: Junaid Shahid <junaids@google.com>
Reviewed-by: David Matlack <dmatlack@google.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220723024316.2725328-1-junaids@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: Junaid Shahid

arch/x86/kvm/mmu/mmu.c

@@ -5361,19 +5361,6 @@ void kvm_mmu_free_obsolete_roots(struct kvm_vcpu *vcpu)
 	__kvm_mmu_free_obsolete_roots(vcpu->kvm, &vcpu->arch.guest_mmu);
 }
 
-static bool need_remote_flush(u64 old, u64 new)
-{
-	if (!is_shadow_present_pte(old))
-		return false;
-	if (!is_shadow_present_pte(new))
-		return true;
-	if ((old ^ new) & SPTE_BASE_ADDR_MASK)
-		return true;
-	old ^= shadow_nx_mask;
-	new ^= shadow_nx_mask;
-	return (old & ~new & SPTE_PERM_MASK) != 0;
-}
-
 static u64 mmu_pte_write_fetch_gpte(struct kvm_vcpu *vcpu, gpa_t *gpa,
 				    int *bytes)
 {
@@ -5519,7 +5506,7 @@ static void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
 			mmu_page_zap_pte(vcpu->kvm, sp, spte, NULL);
 			if (gentry && sp->role.level != PG_LEVEL_4K)
 				++vcpu->kvm->stat.mmu_pde_zapped;
-			if (need_remote_flush(entry, *spte))
+			if (is_shadow_present_pte(entry))
 				flush = true;
 			++spte;
 		}