Re: [Qemu-devel] [PATCH v10 01/19] vfio: Mediated device Core driver

[Jike Song]

On 11/01/2016 11:44 AM, Alex Williamson wrote:
> On Tue, 01 Nov 2016 11:08:15 +0800
> Jike Song <address@hidden> wrote:
>> On 10/27/2016 05:29 AM, Kirti Wankhede wrote:
>>> +static int mdev_attach_iommu(struct mdev_device *mdev)
>>> +{
>>> +   int ret;
>>> +   struct iommu_group *group;
>>> +
>>> +   group = iommu_group_alloc();
>>> +   if (IS_ERR(group))
>>> +           return PTR_ERR(group);  
>>
>> Maybe I overthought, but where the iommu_group is released? On successful
>> return you already have a ref, I didn't find an iommu_group_put after that.
> ...
>>> +
>>> +   ret = iommu_group_add_device(group, &mdev->dev);
>>> +   if (ret)
>>> +           goto attach_fail;
>>> +
>>> +   dev_info(&mdev->dev, "MDEV: group_id = %d\n",
>>> +                            iommu_group_id(group));
>>> +attach_fail:
>>> +   iommu_group_put(group);
>>> +   return ret;
>>> +}
>>> +
>>> +static void mdev_detach_iommu(struct mdev_device *mdev)
>>> +{
>>> +   iommu_group_remove_device(&mdev->dev);
> 
> Here.  Adding a device to the group takes a group reference so we can
> 'put' the group to release the reference from the alloc as soon as a
> device is added.  When we remove the device, that reference is removed
> and this should result in a release of the group if all other
> references are balanced.  Thanks,

Now I understand, thanks :)

--
Thanks,
Jike