This is a note to let you know that I've just added the patch titled PCI: hv: Add pci_destroy_slot() in pci_devices_present_work(), if necessary to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: pci-hv-add-pci_destroy_slot-in-pci_devices_present_w.patch and it can be found in the queue-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit df1a1c65fc7b1b9c9a5341973dd8cd02039368d0 Author: Dexuan Cui <decui@xxxxxxxxxxxxx> Date: Wed May 15 16:06:22 2019 -0700 PCI: hv: Add pci_destroy_slot() in pci_devices_present_work(), if necessary [ Upstream commit 340d455699400f2c2c0f9b3f703ade3085cdb501 ] When we hot-remove a device, usually the host sends us a PCI_EJECT message, and a PCI_BUS_RELATIONS message with bus_rel->device_count == 0. When we execute the quick hot-add/hot-remove test, the host may not send us the PCI_EJECT message if the guest has not fully finished the initialization by sending the PCI_RESOURCES_ASSIGNED* message to the host, so it's potentially unsafe to only depend on the pci_destroy_slot() in hv_eject_device_work() because the code path create_root_hv_pci_bus() -> hv_pci_assign_slots() is not called in this case. Note: in this case, the host still sends the guest a PCI_BUS_RELATIONS message with bus_rel->device_count == 0. In the quick hot-add/hot-remove test, we can have such a race before the code path pci_devices_present_work() -> new_pcichild_device() adds the new device into the hbus->children list, we may have already received the PCI_EJECT message, and since the tasklet handler hv_pci_onchannelcallback() may fail to find the "hpdev" by calling get_pcichild_wslot(hbus, dev_message->wslot.slot) hv_pci_eject_device() is not called; Later, by continuing execution create_root_hv_pci_bus() -> hv_pci_assign_slots() creates the slot and the PCI_BUS_RELATIONS message with bus_rel->device_count == 0 removes the device from hbus->children, and we end up being unable to remove the slot in hv_pci_remove() -> hv_pci_remove_slots() Remove the slot in pci_devices_present_work() when the device is removed to address this race. pci_devices_present_work() and hv_eject_device_work() run in the singled-threaded hbus->wq, so there is not a double-remove issue for the slot. We cannot offload hv_pci_eject_device() from hv_pci_onchannelcallback() to the workqueue, because we need the hv_pci_onchannelcallback() synchronously call hv_pci_eject_device() to poll the channel ringbuffer to work around the "hangs in hv_compose_msi_msg()" issue fixed in commit de0aa7b2f97d ("PCI: hv: Fix 2 hang issues in hv_compose_msi_msg()") Fixes: a15f2c08c708 ("PCI: hv: support reporting serial number as slot information") Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx> [lorenzo.pieralisi@xxxxxxx: rewritten commit log] Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> Reviewed-by: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx> Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c index a5825bbcded72..f591de23f3d35 100644 --- a/drivers/pci/host/pci-hyperv.c +++ b/drivers/pci/host/pci-hyperv.c @@ -1824,6 +1824,10 @@ static void pci_devices_present_work(struct work_struct *work) hpdev = list_first_entry(&removed, struct hv_pci_dev, list_entry); list_del(&hpdev->list_entry); + + if (hpdev->pci_slot) + pci_destroy_slot(hpdev->pci_slot); + put_pcichild(hpdev, hv_pcidev_ref_initial); }