---
 include/linux/kvm_host.h |  2 ++
 virt/kvm/guest_memfd.c   | 31 +++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 3915da2a61778..27687fb9d5201 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h

@@ -2575,6 +2575,8 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
 #endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */

 #ifdef CONFIG_KVM_GUEST_MEMFD
+bool kvm_gmem_is_private(struct kvm *kvm, gfn_t gfn);
+
 int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
                     gfn_t gfn, kvm_pfn_t *pfn, struct page **page,
                     int *max_order);

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 8101f64e0366f..bca912db5be6e 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c

@@ -510,6 +510,37 @@ static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma)
        return 0;
 }

+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, 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,

--

2.55.0.rc0.738.g0c8ab3ebcc-goog