[RFC PATCH v5 13/16] KVM: guest_memfd: Notify providers after private attribute updates

["Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>]

Publish whether committed private ranges remain through an optional
update_private_ranges() provider operation. Scan the attribute tree
after successful publication while holding the inode invalidate lock and
any provider lock.

Keep the cached summary in the provider that uses it. Providers
initialize their summary during attach() before exposing access checks.

Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
 include/linux/guest_memfd.h |  5 +++++
 virt/kvm/guest_memfd.c      | 25 ++++++++++++++++++++++++-
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/include/linux/guest_memfd.h b/include/linux/guest_memfd.h
index ebfb3199a302..31cd5142e5f1 100644
--- a/include/linux/guest_memfd.h
+++ b/include/linux/guest_memfd.h
@@ -76,6 +76,10 @@ struct guest_memfd_handle {
  * @unlock: Release the provider lock taken by lock(). Called after guest
  *          invalidation ends and any successful attribute publication, with
  *          the inode invalidate lock still held.
+ * @update_private_ranges: Optional notification of whether committed private
+ *                         ranges remain. Called after attribute publication,
+ *                         and with false after final file cleanup, under the
+ *                         inode invalidate lock and any provider lock.
  * @prepare_attributes: Optional memory validation before conversion, under
  *                      the inode invalidate lock for write, before taking
  *                      the provider lock or starting guest invalidation. Host mappings have
@@ -144,6 +148,7 @@ struct guest_memfd_provider_operations {
 				     u32 flags);
 	void (*lock)(void *provider);
 	void (*unlock)(void *provider);
+	void (*update_private_ranges)(void *provider, bool has_private_ranges);
 	int (*prepare_attributes)(struct inode *inode, void *provider, pgoff_t start,
 			size_t nr_pages, u64 memory_attrs, pgoff_t *err_index);
 	int (*allocate_range)(struct inode *inode, void *provider,
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index a9609ddccafd..1c90f59f480e 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -1317,6 +1317,27 @@ static int gmem_provider_make_shared(struct inode *inode, pgoff_t start,
 	return 0;
 }
 
+static void gmem_provider_update_attributes(struct inode *inode)
+{
+	struct gmem_inode *gi = GMEM_I(inode);
+	void *entry;
+	bool private = false;
+
+	MA_STATE(mas, &gi->attributes, 0, 0);
+
+	if (!gi->provider_ops->update_private_ranges)
+		return;
+
+	mas_for_each(&mas, entry, ULONG_MAX) {
+		if (kvm_gmem_get_attributes(&gi->vfs_inode, entry) &
+		    KVM_MEMORY_ATTRIBUTE_PRIVATE) {
+			private = true;
+			break;
+		}
+	}
+	gi->provider_ops->update_private_ranges(gi->provider, private);
+}
+
 static int __kvm_gmem_set_attributes(struct inode *inode, pgoff_t start,
 		size_t nr_pages, u64 attrs, pgoff_t *err_index)
 {
@@ -1369,8 +1390,10 @@ static int __kvm_gmem_set_attributes(struct inode *inode, pgoff_t start,
 	if (!to_private)
 		r = gmem_provider_make_shared(inode, start, end);
 
-	if (!r)
+	if (!r) {
 		mas_store_prealloc(&mas, xa_mk_value(attrs));
+		gmem_provider_update_attributes(inode);
+	}
 
 	if (r)
 		mas_destroy(&mas);
-- 
2.43.0