[PATCH RFC v3 62/88] vfio: Dispatch guest_memfd check_set_attributes via vfio_device_ops

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@xxxxxxxxxx>

When userspace requests attribute conversion on a guest_memfd file
backed by a VFIO resource descriptor, guest_memfd invokes the
.check_set_attributes provider operation under the exclusive filemap
invalidation lock before committing attribute changes.

Implement .check_set_attributes on vfio_device_gmem_provider_ops to
dispatch to the bus driver's .gmem_check_set_attributes callback on
struct vfio_device_ops if implemented, allowing the driver to inspect
and validate the requested attributes and offset range.

Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
---
 drivers/vfio/vfio_main.c | 24 ++++++++++++++++++++----
 include/linux/vfio.h     |  3 +++
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
index 979ed69c5ebf7..e4e7bfe77d03b 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -1621,11 +1621,27 @@ static int vfio_device_gmem_mmap(void *provider, struct vm_area_struct *vma)
 	return vfio_device_mmap(df->device, vma);
 }
 
+static int vfio_device_gmem_check_set_attributes(void *provider, pgoff_t index,
+						 size_t nr_pages,
+						 u64 attributes)
+{
+	struct file *file = provider;
+	struct vfio_device_file *df = file->private_data;
+	struct vfio_device *device = df->device;
+
+	if (!device->ops->gmem_check_set_attributes)
+		return 0;
+
+	return device->ops->gmem_check_set_attributes(device, index, nr_pages,
+						      attributes);
+}
+
 static const struct guest_memfd_provider_operations vfio_device_gmem_provider_ops = {
-	.attach  = vfio_device_gmem_attach,
-	.release = vfio_device_gmem_release,
-	.get_pfn = vfio_device_gmem_get_pfn,
-	.mmap    = vfio_device_gmem_mmap,
+	.attach               = vfio_device_gmem_attach,
+	.release              = vfio_device_gmem_release,
+	.get_pfn              = vfio_device_gmem_get_pfn,
+	.mmap                 = vfio_device_gmem_mmap,
+	.check_set_attributes = vfio_device_gmem_check_set_attributes,
 };
 #endif
 
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 51e04b980a381..ffb01e655735f 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -125,6 +125,9 @@ struct vfio_device_ops {
 	int (*gmem_get_pfn)(struct vfio_device *device, pgoff_t index,
 			    unsigned long *pfn, int *max_order,
 			    u64 *pfn_attrs);
+	int (*gmem_check_set_attributes)(struct vfio_device *device,
+					 pgoff_t index, size_t nr_pages,
+					 u64 attributes);
 	char	*name;
 	int	(*init)(struct vfio_device *vdev);
 	void	(*release)(struct vfio_device *vdev);

-- 
2.56.0.455.g6c5a503b38-goog