On 6/19/2026 8:31 AM, Ackerley Tng via B4 Relay wrote:

From: Ackerley Tng <redacted>

Introduce function for KVM to check the private/shared status of guest

           ^
Nit:       a
 > memory at a given GFN.

This will be used in a later patch.

[...]

 
+bool kvm_gmem_is_private(struct kvm *kvm, gfn_t gfn)
+{
+	struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
+	struct inode *inode;
+
+	/*
+	 * If this gfn has no associated memslot, there's no chance of the gfn
+	 * being backed by private memory, since guest_memfd must be used for
+	 * private memory,

"guest_memfd must be used for private memory" is a bit confusing to me.

and guest_memfd must be associated with some memslot.
+	 */
+	if (!slot)
+		return 0;
+
+	CLASS(gmem_get_file, file)(slot);
+	if (!file)
+		return 0;
+
+	inode = file_inode(file);
+
+	/*
+	 * Rely on the maple tree's internal RCU lock to ensure a
+	 * stable result. This result can become stale as soon as the
+	 * lock is dropped, so the caller _must_ still protect
+	 * consumption of private vs. shared by checking
+	 * mmu_invalidate_retry_gfn() under mmu_lock to serialize
+	 * against ongoing attribute updates.
+	 */
+	return kvm_gmem_is_private_mem(inode, kvm_gmem_get_index(slot, gfn));
+}
+EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_is_private);
+
 static struct file_operations kvm_gmem_fops = {
 	.mmap		= kvm_gmem_mmap,
 	.open		= generic_file_open,