From: longli@xxxxxxxxxxxxxxxxx <longli@xxxxxxxxxxxxxxxxx> Sent: Wednesday, May 12, 2021 1:07 AM
>
> On removing the device, any work item (hv_pci_devices_present() or
> hv_pci_eject_device()) scheduled on workqueue hbus->wq may still be running
> and race with hv_pci_remove().
>
> This can happen because the host may send PCI_EJECT or PCI_BUS_RELATIONS(2)
> and decide to rescind the channel immediately after that.
>
> Fix this by flushing/destroying the workqueue of hbus before doing hbus remove.
>
> Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
> ---
> Change in v2: Remove unused bus state hv_pcibus_removed
> Change in v3: Change hv_pci_bus_exit() to not use workqueue to remove PCI devices
>
> drivers/pci/controller/pci-hyperv.c | 30 ++++++++++++++++++++++-------
> 1 file changed, 23 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index 27a17a1e4a7c..c6122a1b0c46 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -444,7 +444,6 @@ enum hv_pcibus_state {
> hv_pcibus_probed,
> hv_pcibus_installed,
> hv_pcibus_removing,
> - hv_pcibus_removed,
> hv_pcibus_maximum
> };
>
> @@ -3247,8 +3246,9 @@ static int hv_pci_bus_exit(struct hv_device *hdev, bool
> keep_devs)
> struct pci_packet teardown_packet;
> u8 buffer[sizeof(struct pci_message)];
> } pkt;
> - struct hv_dr_state *dr;
> struct hv_pci_compl comp_pkt;
> + struct hv_pci_dev *hpdev, *tmp;
> + unsigned long flags;
> int ret;
>
> /*
> @@ -3260,9 +3260,16 @@ static int hv_pci_bus_exit(struct hv_device *hdev, bool
> keep_devs)
>
> if (!keep_devs) {
> /* Delete any children which might still exist. */
> - dr = kzalloc(sizeof(*dr), GFP_KERNEL);
> - if (dr && hv_pci_start_relations_work(hbus, dr))
> - kfree(dr);
> + spin_lock_irqsave(&hbus->device_list_lock, flags);
> + list_for_each_entry_safe(hpdev, tmp, &hbus->children, list_entry) {
> + list_del(&hpdev->list_entry);
> + if (hpdev->pci_slot)
> + pci_destroy_slot(hpdev->pci_slot);
> + /* For the two refs got in new_pcichild_device() */
> + put_pcichild(hpdev);
> + put_pcichild(hpdev);
> + }
> + spin_unlock_irqrestore(&hbus->device_list_lock, flags);
> }
>
> ret = hv_send_resources_released(hdev);
> @@ -3305,13 +3312,23 @@ static int hv_pci_remove(struct hv_device *hdev)
>
> hbus = hv_get_drvdata(hdev);
> if (hbus->state == hv_pcibus_installed) {
> + tasklet_disable(&hdev->channel->callback_event);
> + hbus->state = hv_pcibus_removing;
> + tasklet_enable(&hdev->channel->callback_event);
> + destroy_workqueue(hbus->wq);
> + hbus->wq = NULL;
> + /*
> + * At this point, no work is running or can be scheduled
> + * on hbus-wq. We can't race with hv_pci_devices_present()
> + * or hv_pci_eject_device(), it's safe to proceed.
> + */
> +
> /* Remove the bus from PCI's point of view. */
> pci_lock_rescan_remove();
> pci_stop_root_bus(hbus->pci_bus);
> hv_pci_remove_slots(hbus);
> pci_remove_root_bus(hbus->pci_bus);
> pci_unlock_rescan_remove();
> - hbus->state = hv_pcibus_removed;
> }
>
> ret = hv_pci_bus_exit(hdev, false);
> @@ -3326,7 +3343,6 @@ static int hv_pci_remove(struct hv_device *hdev)
> irq_domain_free_fwnode(hbus->sysdata.fwnode);
> put_hvpcibus(hbus);
> wait_for_completion(&hbus->remove_event);
> - destroy_workqueue(hbus->wq);
>
> hv_put_dom_num(hbus->sysdata.domain);
>
> --
> 2.27.0
Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
