[PATCH 09/21] vfio/pci: Store Live Update state in struct vfio_pci_core_device

[David Matlack <dmatlack@google.com>]

Stash a pointer to a device's Live Updated state in struct
vfio_pci_core_device. This will enable subsequent commits to use the
preserved state when enabling the device.

To enable VFIO to safely access this pointer during device enablement,
require that the device is fully enabled before returning true from
can_finish().

Signed-off-by: David Matlack <dmatlack@google.com>
---
 drivers/vfio/pci/vfio_pci_core.c       |  1 +
 drivers/vfio/pci/vfio_pci_liveupdate.c | 20 +++++++++++++++++++-
 include/linux/vfio_pci_core.h          |  6 ++++++
 3 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 7dcf5439dedc..b09fe0993e04 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -536,6 +536,7 @@ int vfio_pci_core_enable(struct vfio_pci_core_device *vdev)
 	if (!vfio_vga_disabled() && vfio_pci_is_vga(pdev))
 		vdev->has_vga = true;
 
+	vdev->liveupdate_state = NULL;
 
 	return 0;
 
diff --git a/drivers/vfio/pci/vfio_pci_liveupdate.c b/drivers/vfio/pci/vfio_pci_liveupdate.c
index 7669c65bde17..0fb29bd3ae3b 100644
--- a/drivers/vfio/pci/vfio_pci_liveupdate.c
+++ b/drivers/vfio/pci/vfio_pci_liveupdate.c
@@ -145,6 +145,7 @@ static int match_device(struct device *dev, const void *arg)
 static int vfio_pci_liveupdate_retrieve(struct liveupdate_file_op_args *args)
 {
 	struct vfio_pci_core_device_ser *ser;
+	struct vfio_pci_core_device *vdev;
 	struct vfio_device *device;
 	struct folio *folio;
 	struct file *file;
@@ -186,6 +187,9 @@ static int vfio_pci_liveupdate_retrieve(struct liveupdate_file_op_args *args)
 		goto out;
 	}
 
+	vdev = container_of(device, struct vfio_pci_core_device, vdev);
+	vdev->liveupdate_state = ser;
+
 	args->file = file;
 
 out:
@@ -197,7 +201,21 @@ static int vfio_pci_liveupdate_retrieve(struct liveupdate_file_op_args *args)
 
 static bool vfio_pci_liveupdate_can_finish(struct liveupdate_file_op_args *args)
 {
-	return args->retrieved;
+	struct vfio_pci_core_device *vdev;
+	struct vfio_device *device;
+
+	if (!args->retrieved)
+		return false;
+
+	device = vfio_device_from_file(args->file);
+	vdev = container_of(device, struct vfio_pci_core_device, vdev);
+
+	/*
+	 * Ensure VFIO is done using vdev->liveupdate_state, which means its
+	 * safe for vfio_pci_liveupdate_finish() to free it.
+	 */
+	guard(mutex)(&device->dev_set->lock);
+	return !vdev->liveupdate_state;
 }
 
 static void vfio_pci_liveupdate_finish(struct liveupdate_file_op_args *args)
diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
index f541044e42a2..56ff6452562d 100644
--- a/include/linux/vfio_pci_core.h
+++ b/include/linux/vfio_pci_core.h
@@ -94,6 +94,12 @@ struct vfio_pci_core_device {
 	struct vfio_pci_core_device	*sriov_pf_core_dev;
 	struct notifier_block	nb;
 	struct rw_semaphore	memory_lock;
+
+	/*
+	 * State passed by the previous kernel during a Live Update. Only
+	 * safe to access when first opening the device.
+	 */
+	struct vfio_pci_core_device_ser *liveupdate_state;
 };
 
 /* Will be exported for vfio pci drivers usage */
-- 
2.52.0.487.g5c8c507ade-goog