KVM: x86/tdp_mmu: Extract root invalid check from tdx_mmu_next_root()

Extract tdp_mmu_root_match() to check if the root has given types and use
it for the root page table iterator.  It checks only_invalid now.

TDX KVM operates on a shared page table only (Shared-EPT), a mirrored page
table only (Secure-EPT), or both based on the operation.  KVM MMU notifier
operations only on shared page table.  KVM guest_memfd invalidation
operations only on mirrored page table, and so on.  Introduce a centralized
matching function instead of open coding matching logic in the iterator.
The next step is to extend the function to check whether the page is shared
or private

Link: https://lore.kernel.org/kvm/ZivazWQw1oCU8VBC@google.com/
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Message-ID: <20240718211230.1492011-10-rick.p.edgecombe@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: yamahata

arch/x86/kvm/mmu/tdp_mmu.c

@@ -92,6 +92,14 @@ void kvm_tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root)
 	call_rcu(&root->rcu_head, tdp_mmu_free_sp_rcu_callback);
 }
 
+static bool tdp_mmu_root_match(struct kvm_mmu_page *root, bool only_valid)
+{
+	if (only_valid && root->role.invalid)
+		return false;
+
+	return true;
+}
+
 /*
  * Returns the next root after @prev_root (or the first root if @prev_root is
  * NULL).  A reference to the returned root is acquired, and the reference to
@@ -125,7 +133,7 @@ static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
 						   typeof(*next_root), link);
 
 	while (next_root) {
-		if ((!only_valid || !next_root->role.invalid) &&
+		if (tdp_mmu_root_match(next_root, only_valid) &&
 		    kvm_tdp_mmu_get_root(next_root))
 			break;
 
@@ -176,7 +184,7 @@ static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
 	list_for_each_entry(_root, &_kvm->arch.tdp_mmu_roots, link)		\
 		if (kvm_lockdep_assert_mmu_lock_held(_kvm, false) &&		\
 		    ((_as_id >= 0 && kvm_mmu_page_as_id(_root) != _as_id) ||	\
-		     ((_only_valid) && (_root)->role.invalid))) {		\
+		     !tdp_mmu_root_match((_root), (_only_valid)))) {		\
 		} else
 
 #define for_each_tdp_mmu_root(_kvm, _root, _as_id)			\