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    SubjectRe: [PATCH 1/8] pci: Make sriov work with hotplug removal
    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.
    --
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