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PCI: hv: Serialize the present and eject work items

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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: 4daace0d8c ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V VMs")
Link: https://lkml.kernel.org/r/KL1P15301MB00064DA6B4D221123B5241CFBFD70@KL1P15301MB0006.APCP153.PROD.OUTLOOK.COM
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>
This commit is contained in:
Dexuan Cui 2018-03-15 14:20:53 +00:00 committed by Lorenzo Pieralisi
parent 7928b2cbe5
commit 021ad274d7
1 changed files with 16 additions and 18 deletions
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34
drivers/pci/host/pci-hyperv.c
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@ -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;
}