The patch below does not apply to the 4.9-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@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 021ad274d7dc31611d4f47f7dd4ac7a224526f30 Mon Sep 17 00:00:00 2001
From: Dexuan Cui decui@microsoft.com Date: Thu, 15 Mar 2018 14:20:53 +0000 Subject: [PATCH] PCI: hv: Serialize the present and eject work items
When we hot-remove the device, we first receive a PCI_EJECT message and then receive a PCI_BUS_RELATIONS message with bus_rel->device_count == 0.
The first message is offloaded to hv_eject_device_work(), and the second is offloaded to pci_devices_present_work(). Both the paths can be running list_del(&hpdev->list_entry), causing general protection fault, because system_wq can run them concurrently.
The patch eliminates the race condition.
Since access to present/eject work items is serialized, we do not need the hbus->enum_sem anymore, so remove it.
Fixes: 4daace0d8ce8 ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V VMs") Link: https://lkml.kernel.org/r/KL1P15301MB00064DA6B4D221123B5241CFBFD70@KL1P15301... Tested-by: Adrian Suhov v-adsuho@microsoft.com Tested-by: Chris Valean v-chvale@microsoft.com Signed-off-by: Dexuan Cui decui@microsoft.com [lorenzo.pieralisi@arm.com: squashed semaphore removal patch] Signed-off-by: Lorenzo Pieralisi lorenzo.pieralisi@arm.com Reviewed-by: Michael Kelley mikelley@microsoft.com Acked-by: Haiyang Zhang haiyangz@microsoft.com Cc: stable@vger.kernel.org # v4.6+ Cc: Vitaly Kuznetsov vkuznets@redhat.com Cc: Jack Morgenstein jackm@mellanox.com Cc: Stephen Hemminger sthemmin@microsoft.com Cc: K. Y. Srinivasan kys@microsoft.com
diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c index 2faf38eab785..b7fd5c157d73 100644 --- a/drivers/pci/host/pci-hyperv.c +++ b/drivers/pci/host/pci-hyperv.c @@ -447,7 +447,6 @@ struct hv_pcibus_device { spinlock_t device_list_lock; /* Protect lists below */ void __iomem *cfg_addr;
- struct semaphore enum_sem; struct list_head resources_for_children;
struct list_head children; @@ -461,6 +460,8 @@ struct hv_pcibus_device { struct retarget_msi_interrupt retarget_msi_interrupt_params;
spinlock_t retarget_msi_interrupt_lock; + + struct workqueue_struct *wq; };
/* @@ -1590,12 +1591,8 @@ static struct hv_pci_dev *get_pcichild_wslot(struct hv_pcibus_device *hbus, * It must also treat the omission of a previously observed device as * notification that the device no longer exists. * - * Note that this function is a work item, and it may not be - * invoked in the order that it was queued. Back to back - * updates of the list of present devices may involve queuing - * multiple work items, and this one may run before ones that - * were sent later. As such, this function only does something - * if is the last one in the queue. + * Note that this function is serialized with hv_eject_device_work(), + * because both are pushed to the ordered workqueue hbus->wq. */ static void pci_devices_present_work(struct work_struct *work) { @@ -1616,11 +1613,6 @@ static void pci_devices_present_work(struct work_struct *work)
INIT_LIST_HEAD(&removed);
- if (down_interruptible(&hbus->enum_sem)) { - put_hvpcibus(hbus); - return; - } - /* Pull this off the queue and process it if it was the last one. */ spin_lock_irqsave(&hbus->device_list_lock, flags); while (!list_empty(&hbus->dr_list)) { @@ -1637,7 +1629,6 @@ static void pci_devices_present_work(struct work_struct *work) spin_unlock_irqrestore(&hbus->device_list_lock, flags);
if (!dr) { - up(&hbus->enum_sem); put_hvpcibus(hbus); return; } @@ -1724,7 +1715,6 @@ static void pci_devices_present_work(struct work_struct *work) break; }
- up(&hbus->enum_sem); put_hvpcibus(hbus); kfree(dr); } @@ -1770,7 +1760,7 @@ static void hv_pci_devices_present(struct hv_pcibus_device *hbus, spin_unlock_irqrestore(&hbus->device_list_lock, flags);
get_hvpcibus(hbus); - schedule_work(&dr_wrk->wrk); + queue_work(hbus->wq, &dr_wrk->wrk); }
/** @@ -1848,7 +1838,7 @@ static void hv_pci_eject_device(struct hv_pci_dev *hpdev) get_pcichild(hpdev, hv_pcidev_ref_pnp); INIT_WORK(&hpdev->wrk, hv_eject_device_work); get_hvpcibus(hpdev->hbus); - schedule_work(&hpdev->wrk); + queue_work(hpdev->hbus->wq, &hpdev->wrk); }
/** @@ -2461,13 +2451,18 @@ static int hv_pci_probe(struct hv_device *hdev, spin_lock_init(&hbus->config_lock); spin_lock_init(&hbus->device_list_lock); spin_lock_init(&hbus->retarget_msi_interrupt_lock); - sema_init(&hbus->enum_sem, 1); init_completion(&hbus->remove_event); + hbus->wq = alloc_ordered_workqueue("hv_pci_%x", 0, + hbus->sysdata.domain); + if (!hbus->wq) { + ret = -ENOMEM; + goto free_bus; + }
ret = vmbus_open(hdev->channel, pci_ring_size, pci_ring_size, NULL, 0, hv_pci_onchannelcallback, hbus); if (ret) - goto free_bus; + goto destroy_wq;
hv_set_drvdata(hdev, hbus);
@@ -2536,6 +2531,8 @@ static int hv_pci_probe(struct hv_device *hdev, hv_free_config_window(hbus); close: vmbus_close(hdev->channel); +destroy_wq: + destroy_workqueue(hbus->wq); free_bus: free_page((unsigned long)hbus); return ret; @@ -2615,6 +2612,7 @@ 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); free_page((unsigned long)hbus); return 0; }