Re: [Qemu-devel] [PATCH v2 2/3] hw/pci: add teardown function for PCI resource reserve capability

["Liu, Jing2" <jing2.liu@linux.intel.com>]

Hi Marcel,

On 8/20/2018 9:38 PM, Marcel Apfelbaum wrote:
> Hi Jing,
> 
> On 08/20/2018 05:58 AM, Liu, Jing2 wrote:
>> Hi Marcel,
>>
>> On 8/18/2018 12:10 AM, Marcel Apfelbaum wrote:
>>> Hi Jing,
>>>
>>> On 08/16/2018 12:28 PM, Jing Liu wrote:
>>>> Clean up the PCI config space of resource reserve capability.
>>>>
>>>> Signed-off-by: Jing Liu <jing2.liu@linux.intel.com>
>>>> ---
>>>>   hw/pci/pci_bridge.c         | 9 +++++++++
>>>>   include/hw/pci/pci_bridge.h | 1 +
>>>>   2 files changed, 10 insertions(+)
>>>>
>>>> diff --git a/hw/pci/pci_bridge.c b/hw/pci/pci_bridge.c
>>>> index 15b055e..dbcee90 100644
>>>> --- a/hw/pci/pci_bridge.c
>>>> +++ b/hw/pci/pci_bridge.c
>>>> @@ -465,6 +465,15 @@ int pci_bridge_qemu_reserve_cap_init(PCIDevice 
>>>> *dev, int cap_offset,
>>>>       return 0;
>>>>   }
>>>> +void pci_bridge_qemu_reserve_cap_uninit(PCIDevice *dev)
>>>> +{
>>>> +    uint8_t pos = pci_find_capability(dev, PCI_CAP_ID_VNDR);
>>>> +
>>>> +    pci_del_capability(dev, PCI_CAP_ID_VNDR, 
>>>> sizeof(PCIBridgeQemuCap));
>>>
>>> I think that you only need to call pci_del_capability,
>>>
>>>> +    memset(dev->config + pos + PCI_CAP_FLAGS, 0,
>>>> +           sizeof(PCIBridgeQemuCap) - PCI_CAP_FLAGS);
>>>> +}
>>>
>>> ... no need for the above line. The reason is pci_del_capability
>>> will "unlink" the capability, and even if the data remains in
>>> the configuration space array, it will not be used.
>>>
>> I think I got it: pci_del_capability "unlink" by set the tag
>> pdev->config[PCI_STATUS] &= ~PCI_STATUS_CAP_LIST;
>> so that pdev->config will not be used, right?
> 
> If is the latest capability in the list, yes.
> Otherwise it will simply link 'prev' with 'next' using config array 
> offsets.
I got it! Thanks very much for the details!

Jing

> 
> Thanks,
> Marcel
> 
>>
>>> Do you agree? If yes, just call pci_del_capability and you don't need
>>> this patch.
>>>
>> Yup, I agree with you. And let me remove this patch in next version.
>>
>> Thanks,
>> Jing
>>
>>>
>>> Thanks,
>>> Marcel
>>>
>>
>> [...]
>