On Wed, May 15, 2019 at 11:20:45PM +0000, Dexuan Cui wrote:
From: gregkh@xxxxxxxxxxxxxxxxxxx <gregkh@xxxxxxxxxxxxxxxxxxx> Sent: Wednesday, May 15, 2019 1:36 AM To: Dexuan Cui <decui@xxxxxxxxxxxxx>; lorenzo.pieralisi@xxxxxxx; Michael Kelley <mikelley@xxxxxxxxxxxxx>; stephen@xxxxxxxxxxxxxxxxxx Cc: stable@xxxxxxxxxxxxxxx Subject: FAILED: patch "[PATCH] PCI: hv: Add pci_destroy_slot() in" failed to apply to 4.14-stable tree The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 340d455699400f2c2c0f9b3f703ade3085cdb501 Mon Sep 17 00:00:00 2001 From: Dexuan Cui <decui@xxxxxxxxxxxxx> Date: Mon, 4 Mar 2019 21:34:49 +0000 Subject: [PATCH] PCI: hv: Add pci_destroy_slot() in pci_devices_present_work(), if necessary 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 diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c index b489412e3502..82acd6155adf 100644 --- a/drivers/pci/controller/pci-hyperv.c +++ b/drivers/pci/controller/pci-hyperv.c @@ -1776,6 +1776,10 @@ 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); }Hi, I backported the patch for linux-4.14.y. Please use the attached patch, which is [PATCH 3/3] Thanks, -- Dexuan
Queued for 4.14, thank you. -- Thanks, Sasha
