[PATCH v4 06/16] vfio/pci: Store incoming Live Update state in struct vfio_pci_core_device

[Vipin Sharma <vipinsh@google.com>]

From: David Matlack <dmatlack@google.com>

Stash a pointer to a device's incoming Live Updated state in struct
vfio_pci_core_device. This will enable subsequent commits to use the
preserved state when initializing 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(). This is synchronized by vfio_pci_core.c setting
vdev->liveupdate_incoming_state to NULL under dev_set lock once it's
done using it.

Signed-off-by: David Matlack <dmatlack@google.com>
Signed-off-by: Vipin Sharma <vipinsh@google.com>
---
 drivers/vfio/pci/vfio_pci_core.c       |  2 +-
 drivers/vfio/pci/vfio_pci_liveupdate.c | 17 ++++++++++++++++-
 include/linux/vfio_pci_core.h          |  2 ++
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 1726d4d41b57..da013b4b1e94 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -568,7 +568,7 @@ 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_incoming_state = NULL;
 	return 0;
 
 out_free_zdev:
diff --git a/drivers/vfio/pci/vfio_pci_liveupdate.c b/drivers/vfio/pci/vfio_pci_liveupdate.c
index 731a3e34085f..7b841a1e7fcc 100644
--- a/drivers/vfio/pci/vfio_pci_liveupdate.c
+++ b/drivers/vfio/pci/vfio_pci_liveupdate.c
@@ -249,6 +249,7 @@ 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 file *file;
 	int ret = 0;
@@ -265,6 +266,9 @@ 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_incoming_state = ser;
+
 	args->file = file;
 out:
 	/* Drop the reference from vfio_find_device() */
@@ -274,7 +278,18 @@ 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->retrieve_status > 0;
+	struct vfio_pci_core_device *vdev;
+	struct vfio_device *device;
+
+	if (args->retrieve_status <= 0)
+		return false;
+
+	device = vfio_device_from_file(args->file);
+	vdev = container_of(device, struct vfio_pci_core_device, vdev);
+
+	/* Check that vdev->liveupdate_incoming_state is no longer in use. */
+	guard(mutex)(&device->dev_set->lock);
+	return !vdev->liveupdate_incoming_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 2ebba746c18f..0c508dd8d1ac 100644
--- a/include/linux/vfio_pci_core.h
+++ b/include/linux/vfio_pci_core.h
@@ -26,6 +26,7 @@
 #define VFIO_PCI_OFFSET_MASK	(((u64)(1) << VFIO_PCI_OFFSET_SHIFT) - 1)
 
 struct vfio_pci_core_device;
+struct vfio_pci_core_device_ser;
 struct vfio_pci_region;
 struct p2pdma_provider;
 struct dma_buf_attachment;
@@ -142,6 +143,7 @@ struct vfio_pci_core_device {
 	struct notifier_block	nb;
 	struct rw_semaphore	memory_lock;
 	struct list_head	dmabufs;
+	struct vfio_pci_core_device_ser *liveupdate_incoming_state;
 };
 
 enum vfio_pci_io_width {
-- 
2.54.0.563.g4f69b47b94-goog