> From: Winiarski, Michal <[email protected]>
> Sent: Thursday, November 20, 2025 8:37 PM
>
> Resetting the migration device state is typically delegated to PCI
> .reset_done() callback.
> With VFIO, reset is usually called under vdev->memory_lock, which causes
> lockdep to report a following circular locking dependency scenario:
>
> 0: set_device_state
> driver->state_mutex -> migf->lock
> 1: data_read
> migf->lock -> mm->mmap_lock
> 2: vfio_pin_dma
> mm->mmap_lock -> vdev->memory_lock
> 3: vfio_pci_ioctl_reset
> vdev->memory_lock -> driver->state_mutex
>
> Introduce a .migration_reset_state() callback called outside of
> vdev->memory_lock to break the dependency chain.
so it kind of unifies the deferred_reset logic cross all drivers.
sounds reasonable as nobody should expect a concrete sequence of
a reset done vs. a racing set_device_state.
>
> +static void vfio_pci_dev_migration_reset_state(struct vfio_pci_core_device
> *vdev)
> +{
> + lockdep_assert_not_held(&vdev->memory_lock);
> +
> + if (!vdev->vdev.mig_ops->migration_reset_state)
> + return;
mig_ops could be NULL.
> @@ -1230,6 +1242,8 @@ static int vfio_pci_ioctl_reset(struct
> vfio_pci_core_device *vdev,
> ret = pci_try_reset_function(vdev->pdev);
> up_write(&vdev->memory_lock);
>
> + vfio_pci_dev_migration_reset_state(vdev);
> +
only if the previous reset succeeds.
> @@ -2486,8 +2501,10 @@ static int vfio_pci_dev_set_hot_reset(struct
> vfio_device_set *dev_set,
>
> err_undo:
> list_for_each_entry_from_reverse(vdev, &dev_set->device_list,
> - vdev.dev_set_list)
> + vdev.dev_set_list) {
> up_write(&vdev->memory_lock);
> + vfio_pci_dev_migration_reset_state(vdev);
> + }
ditto
btw some reset paths are missed in drivers/vfio/pci/vfio_pci_config.c,
e.g. for vFLR emulation.
