Re: [PATCH 1/8] pci: Make sriov work with hotplug removal

[Yinghai Lu <yinghai.lu@oracle.com>]

On 10/17/2011 10:16 AM, Bjorn Helgaas wrote:
> On Sat, Oct 15, 2011 at 7:31 PM, Yinghai Lu<yinghai.lu@oracle.com>  wrote:
>>
>> When hot remove pci express module, got
>>
>> [ 5918.610127] pciehp 0000:80:02.2:pcie04: pcie_isr: intr_loc 1
>> [ 5918.615779] pciehp 0000:80:02.2:pcie04: Attention button interrupt received
>> [ 5918.622730] pciehp 0000:80:02.2:pcie04: Button pressed on Slot(3)
>> [ 5918.629002] pciehp 0000:80:02.2:pcie04: pciehp_get_power_status: SLOTCTRL a8 value read 1f9
>> [ 5918.637416] pciehp 0000:80:02.2:pcie04: PCI slot #3 - powering off due to button press.
>> [ 5918.647125] pciehp 0000:80:02.2:pcie04: pcie_isr: intr_loc 10
>> [ 5918.653039] pciehp 0000:80:02.2:pcie04: pciehp_green_led_blink: SLOTCTRL a8 write cmd 200
>> [ 5918.661229] pciehp 0000:80:02.2:pcie04: pciehp_set_attention_status: SLOTCTRL a8 write cmd c0
>> [ 5924.667627] pciehp 0000:80:02.2:pcie04: Disabling domain:bus:device=0000:b0:00
>> [ 5924.674909] pciehp 0000:80:02.2:pcie04: pciehp_get_power_status: SLOTCTRL a8 value read 2f9
>> [ 5924.683262] pciehp 0000:80:02.2:pcie04: pciehp_unconfigure_device: domain:bus:dev = 0000:b0:00
>> [ 5924.693976] libfcoe_device_notification: NETDEV_UNREGISTER eth6
>> [ 5924.764979] libfcoe_device_notification: NETDEV_UNREGISTER eth14
>> [ 5924.873539] libfcoe_device_notification: NETDEV_UNREGISTER eth15
>> [ 5924.995209] libfcoe_device_notification: NETDEV_UNREGISTER eth16
>> [ 5926.114407] sxge 0000:b2:00.0: PCI INT A disabled
>> [ 5926.119342] BUG: unable to handle kernel NULL pointer dereference at (null)
>> [ 5926.127189] IP: [<ffffffff81353a3b>] pci_stop_bus_device+0x33/0x83
>> [ 5926.133377] PGD 0
>> [ 5926.135402] Oops: 0000 [#1] SMP
>> [ 5926.138659] CPU 2
>> [ 5926.140499] Modules linked in:
>> ...
>> [ 5926.143754]
>> [ 5926.275823] Call Trace:
>> [ 5926.278267]  [<ffffffff81353a38>] pci_stop_bus_device+0x30/0x83
>> [ 5926.284180]  [<ffffffff81353af4>] pci_remove_bus_device+0x1a/0xba
>> [ 5926.290264]  [<ffffffff81366311>] pciehp_unconfigure_device+0x110/0x17b
>> [ 5926.296866]  [<ffffffff81365dd9>] ? pciehp_disable_slot+0x188/0x188
>> [ 5926.303123]  [<ffffffff81365d6f>] pciehp_disable_slot+0x11e/0x188
>> [ 5926.309206]  [<ffffffff81365e68>] pciehp_power_thread+0x8f/0xe0
>> ...
>>
>> Root cause: when doing pci_stop_bus_device() with phys fn, it will stop virt fn and
>> remove the fn, so
>>         list_for_each_safe(l, n,&bus->devices)
>> will have problem to refer freed n that is pointed to vf entry.
>>
>> Solution is just call pci_stop_bus_device() with phys fn only. and before that need to
>> save phys fn aside and avoid to use bus->devices to loop.
>>
>> Signed-off-by: Yinghai Lu<yinghai@kernel.org>
>>
>> ---
>>   drivers/pci/remove.c |   33 +++++++++++++++++++++++++++++++++
>>   1 file changed, 33 insertions(+)
>>
>> Index: linux-2.6/drivers/pci/remove.c
>> ===================================================================
>> --- linux-2.6.orig/drivers/pci/remove.c
>> +++ linux-2.6/drivers/pci/remove.c
>> @@ -120,10 +120,43 @@ void pci_remove_behind_bridge(struct pci
>>                         pci_remove_bus_device(pci_dev_b(l));
>>   }
>>
>> +struct dev_list {
>> +       struct pci_dev *dev;
>> +       struct list_head list;
>> +};
>> +
>>   static void pci_stop_bus_devices(struct pci_bus *bus)
>>   {
>>         struct list_head *l, *n;
>> +       struct dev_list *dl, *dn;
>> +       LIST_HEAD(physfn_list);
>> +
>> +       /* Save phys_fn aside at first */
>> +       list_for_each(l,&bus->devices) {
>> +               struct pci_dev *dev = pci_dev_b(l);
>> +
>> +               if (!dev->is_virtfn) {
>> +                       dl = kmalloc(sizeof(*dl), GFP_KERNEL);
>> +                       if (!dl)
>> +                               continue;
>> +                       dl->dev = dev;
>> +                       list_add_tail(&dl->list,&physfn_list);
>> +               }
>> +       }
>> +
>> +       /*
>> +        * stop bus device for phys_fn at first
>> +        *  it will stop and remove vf in driver remove action
>> +        */
>> +       list_for_each_entry_safe(dl, dn,&physfn_list, list) {
>> +               struct pci_dev *dev = dl->dev;
>> +
>> +               pci_stop_bus_device(dev);
>> +
>> +               kfree(dl);
>> +       }
>>
>> +       /* Do it again for left over in case */
>>         list_for_each_safe(l, n,&bus->devices) {
>>                 struct pci_dev *dev = pci_dev_b(l);
>>                 pci_stop_bus_device(dev);
>
> Apparently it's a problem to stop a VF before its PF?  Why is that?
> Sounds like there's an important dependency here, but I can't figure
> it out.  I would have naively expected that you would *want* to stop a
> VF first, since it depends on the PF.

when you stop the VF, that VF will not be removed.

when you stop the PF, the driver will be unloaded, it will *STOP* the VF 
at first and *REMOVE* the VF there. So the bus->devices will be touch at 
that time.
for example when you have three VFs. those VFs will be removed from 
bus->devices, and n in the list_for_each_safe will have invalid pointer 
to freed entry.

So stop the VF at first will *NOT* help.

Thanks

Yinghai