Notify the PCI subsystem about devices vfio-pci is preserving across
Live Update by registering the vfio-pci liveupdate file handler with the
PCI subsystem's FLB handler.

Notably this will ensure that devices preserved through vfio-pci do not
go through auto-probing in the next kernel (i.e. preventing them from
being bound to a different driver).

This also enables VFIO to detect that a device was preserved before
userspace first retrieves the file from it, which will be used in
subsequent commits.

Signed-off-by: David Matlack <dmatlack@google.com>
---
 drivers/vfio/pci/vfio_pci_liveupdate.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/pci/vfio_pci_liveupdate.c b/drivers/vfio/pci/vfio_pci_liveupdate.c
index b7451007fca4..7669c65bde17 100644
--- a/drivers/vfio/pci/vfio_pci_liveupdate.c
+++ b/drivers/vfio/pci/vfio_pci_liveupdate.c
@@ -64,6 +64,7 @@ static int vfio_pci_liveupdate_preserve(struct liveupdate_file_op_args *args)
 	if (err)
 		goto error;
 
+	pci_liveupdate_outgoing_preserve(pdev);
 	args->serialized_data = virt_to_phys(ser);
 	return 0;
 
@@ -75,8 +76,10 @@ static int vfio_pci_liveupdate_preserve(struct liveupdate_file_op_args *args)
 static void vfio_pci_liveupdate_unpreserve(struct liveupdate_file_op_args *args)
 {
 	struct vfio_pci_core_device_ser *ser = phys_to_virt(args->serialized_data);
+	struct vfio_device *device = vfio_device_from_file(args->file);
 	struct folio *folio = virt_to_folio(ser);
 
+	pci_liveupdate_outgoing_unpreserve(to_pci_dev(device->dev));
 	kho_unpreserve_folio(folio);
 	folio_put(folio);
 }
@@ -199,8 +202,11 @@ static bool vfio_pci_liveupdate_can_finish(struct liveupdate_file_op_args *args)
 
 static void vfio_pci_liveupdate_finish(struct liveupdate_file_op_args *args)
 {
+	struct vfio_device *device = vfio_device_from_file(args->file);
 	struct folio *folio;
 
+	pci_liveupdate_incoming_finish(to_pci_dev(device->dev));
+
 	folio = virt_to_folio(phys_to_virt(args->serialized_data));
 	folio_put(folio);
 }
@@ -223,10 +229,24 @@ static struct liveupdate_file_handler vfio_pci_liveupdate_fh = {
 
 int __init vfio_pci_liveupdate_init(void)
 {
+	int ret;
+
 	if (!liveupdate_enabled())
 		return 0;
 
-	return liveupdate_register_file_handler(&vfio_pci_liveupdate_fh);
+	ret = liveupdate_register_file_handler(&vfio_pci_liveupdate_fh);
+	if (ret)
+		return ret;
+
+	ret = pci_liveupdate_register_fh(&vfio_pci_liveupdate_fh);
+	if (ret)
+		goto error;
+
+	return 0;
+
+error:
+	liveupdate_unregister_file_handler(&vfio_pci_liveupdate_fh);
+	return ret;
 }
 
 void vfio_pci_liveupdate_cleanup(void)
@@ -234,5 +254,6 @@ void vfio_pci_liveupdate_cleanup(void)
 	if (!liveupdate_enabled())
 		return;
 
+	WARN_ON_ONCE(pci_liveupdate_unregister_fh(&vfio_pci_liveupdate_fh));
 	liveupdate_unregister_file_handler(&vfio_pci_liveupdate_fh);
 }
-- 
2.52.0.487.g5c8c507ade-goog