diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 3ad0719bfc4f..601bbcaa5e41 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -728,6 +728,17 @@ static inline bool kvm_arch_has_private_mem(struct kvm *kvm)
 }
 #endif
 
+/*
+ * Arch code must define kvm_arch_gmem_supports_shared_mem if support for
+ * private memory is enabled and it supports in-place shared/private conversion.
+ */
+#if !defined(kvm_arch_gmem_supports_shared_mem) && !IS_ENABLED(CONFIG_KVM_GMEM_SHARED_MEM)
+static inline bool kvm_arch_gmem_supports_shared_mem(struct kvm *kvm)
+{
+	return false;
+}
+#endif
+
 #ifndef kvm_arch_has_readonly_mem
 static inline bool kvm_arch_has_readonly_mem(struct kvm *kvm)
 {
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 45e6d8fca9b9..117937a895da 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -929,6 +929,7 @@ struct kvm_enable_cap {
 #define KVM_CAP_PRE_FAULT_MEMORY 236
 #define KVM_CAP_X86_APIC_BUS_CYCLES_NS 237
 #define KVM_CAP_X86_GUEST_MODE 238
+#define KVM_CAP_GMEM_SHARED_MEM 239
 
 struct kvm_irq_routing_irqchip {
 	__u32 irqchip;
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 5fc414becae5..eea44e003ed1 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -320,7 +320,109 @@ static pgoff_t kvm_gmem_get_index(struct kvm_memory_slot *slot, gfn_t gfn)
 	return gfn - slot->base_gfn + slot->gmem.pgoff;
 }
 
+#ifdef CONFIG_KVM_GMEM_SHARED_MEM
+static bool folio_offset_is_shared(const struct folio *folio, struct file *file, pgoff_t index)
+{
+	struct kvm_gmem *gmem = file->private_data;
+
+	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
+
+	/* For now, VMs that support shared memory share all their memory. */
+	return kvm_arch_gmem_supports_shared_mem(gmem->kvm);
+}
+
+static vm_fault_t kvm_gmem_fault(struct vm_fault *vmf)
+{
+	struct inode *inode = file_inode(vmf->vma->vm_file);
+	struct folio *folio;
+	vm_fault_t ret = VM_FAULT_LOCKED;
+
+	filemap_invalidate_lock_shared(inode->i_mapping);
+
+	folio = kvm_gmem_get_folio(inode, vmf->pgoff);
+	if (IS_ERR(folio)) {
+		int err = PTR_ERR(folio);
+
+		if (err == -EAGAIN)
+			ret = VM_FAULT_RETRY;
+		else
+			ret = vmf_error(err);
+
+		goto out_filemap;
+	}
+
+	if (folio_test_hwpoison(folio)) {
+		ret = VM_FAULT_HWPOISON;
+		goto out_folio;
+	}
+
+	if (!folio_offset_is_shared(folio, vmf->vma->vm_file, vmf->pgoff)) {
+		ret = VM_FAULT_SIGBUS;
+		goto out_folio;
+	}
+
+	/*
+	 * Shared folios would not be marked as "guestmem" so far, and we only
+	 * expect shared folios at this point.
+	 */
+	if (WARN_ON_ONCE(folio_test_guestmem(folio)))  {
+		ret = VM_FAULT_SIGBUS;
+		goto out_folio;
+	}
+
+	/* No support for huge pages. */
+	if (WARN_ON_ONCE(folio_test_large(folio))) {
+		ret = VM_FAULT_SIGBUS;
+		goto out_folio;
+	}
+
+	if (!folio_test_uptodate(folio)) {
+		clear_highpage(folio_page(folio, 0));
+		kvm_gmem_mark_prepared(folio);
+	}
+
+	vmf->page = folio_file_page(folio, vmf->pgoff);
+
+out_folio:
+	if (ret != VM_FAULT_LOCKED) {
+		folio_unlock(folio);
+		folio_put(folio);
+	}
+
+out_filemap:
+	filemap_invalidate_unlock_shared(inode->i_mapping);
+
+	return ret;
+}
+
+static const struct vm_operations_struct kvm_gmem_vm_ops = {
+	.fault = kvm_gmem_fault,
+};
+
+static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	struct kvm_gmem *gmem = file->private_data;
+
+	if (!kvm_arch_gmem_supports_shared_mem(gmem->kvm))
+		return -ENODEV;
+
+	if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) !=
+	    (VM_SHARED | VM_MAYSHARE)) {
+		return -EINVAL;
+	}
+
+	file_accessed(file);
+	vm_flags_set(vma, VM_DONTDUMP);
+	vma->vm_ops = &kvm_gmem_vm_ops;
+
+	return 0;
+}
+#else
+#define kvm_gmem_mmap NULL
+#endif /* CONFIG_KVM_GMEM_SHARED_MEM */
+
 static struct file_operations kvm_gmem_fops = {
+	.mmap		= kvm_gmem_mmap,
 	.open		= generic_file_open,
 	.release	= kvm_gmem_release,
 	.fallocate	= kvm_gmem_fallocate,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index ba0327e2d0d3..38f0f402ea46 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4830,6 +4830,10 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
 #ifdef CONFIG_KVM_PRIVATE_MEM
 	case KVM_CAP_GUEST_MEMFD:
 		return !kvm || kvm_arch_has_private_mem(kvm);
+#endif
+#ifdef CONFIG_KVM_GMEM_SHARED_MEM
+	case KVM_CAP_GMEM_SHARED_MEM:
+		return !kvm || kvm_arch_gmem_supports_shared_mem(kvm);
 #endif
 	default:
 		break;
