Re: [Qemu-devel] [PATCH v3] pci: clean all funcs when hot-removing multifunc device

[Amos Kong]

On 05/11/2012 02:55 AM, Michael S. Tsirkin wrote:
> On Fri, May 11, 2012 at 01:09:13AM +0800, Jiang Liu wrote:
>> On 05/10/2012 11:44 PM, Amos Kong wrote:
>>
>>> diff --git a/drivers/pci/hotplug/acpiphp_glue.c 
>>> b/drivers/pci/hotplug/acpiphp_glue.c
>>> index 806c44f..a7442d9 100644
>>> --- a/drivers/pci/hotplug/acpiphp_glue.c
>>> +++ b/drivers/pci/hotplug/acpiphp_glue.c
>>> @@ -885,7 +885,7 @@ static void disable_bridges(struct pci_bus *bus)
>>>  static int disable_device(struct acpiphp_slot *slot)
>>>  {
>>>     struct acpiphp_func *func;
>>> -   struct pci_dev *pdev;
>>> +   struct pci_dev *pdev, *tmp;
>>>     struct pci_bus *bus = slot->bridge->pci_bus;
>>>  
>>>     /* The slot will be enabled when func 0 is added, so check
>>> @@ -902,9 +902,10 @@ static int disable_device(struct acpiphp_slot *slot)
>>>                     func->bridge = NULL;
>>>             }
>>>  
>>> -           pdev = pci_get_slot(slot->bridge->pci_bus,
>>> -                               PCI_DEVFN(slot->device, func->function));
>>> -           if (pdev) {
>>> +           list_for_each_entry_safe(pdev, tmp, &bus->devices, bus_list) {
>>> +                   if (PCI_SLOT(pdev->devfn) != slot->device)
>>> +                           continue;
>>> +
>> The pci_bus_sem lock should be acquired when walking the bus->devices list.
>> Otherwise it may cause invalid memory access if another thread is modifying
>> the bus->devices list concurrently.


>> BTW, what's the relationship with "[PATCH v3] hotplug: add device per func
>> in ACPI DSDT tables"? Seems they are both solving the same issue.

Two work need to be done when we disable a slot, cleaning
configuration(in OS) and power off slot.

Currently the second part(power off) works fine, all funcs disappear
from "(qemu)#info block" after hot-remove slot.
The only problem is func 1~7 are not unconfigured, so I NAKed seabios
patch, and try to fix this problem in pci driver.

(btw, winxp & win7 hotplug works currently)

/**
 * acpiphp_disable_slot - power off slot
 * @slot: ACPI PHP slot
 */
int acpiphp_disable_slot(struct acpiphp_slot *slot)
{
        mutex_lock(&slot->crit_sect);

        /* unconfigure all functions */
        retval = disable_device(slot);

        /* power off all functions */
        retval = power_off_slot(slot);
        ....
}

> That's a bios patch. It's needed if you want broken linux to work.  This
> makes linux behave properly on the original bios.
> 
>>>                     pci_stop_bus_device(pdev);
>>>                     if (pdev->subordinate) {
>>>                             disable_bridges(pdev->subordinate);



-- 
                        Amos.