From mboxrd@z Thu Jan  1 00:00:00 1970
From: Xiao Guangrong <guangrong.xiao@intel.com>
Subject: Re: [Qemu-devel] [PATCH 1/2] KVM: page track: add a new notifier
 type: track_flush_slot
Date: Wed, 19 Oct 2016 13:45:29 +0800
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Cc: "Tian, Kevin" <kevin.tian@intel.com>, Neo Jia <cjia@nvidia.com>,
        kvm@vger.kernel.org,
        Xiao Guangrong <guangrong.xiao@linux.intel.com>,
        qemu-devel <qemu-devel@nongnu.org>,
        Xiaoguang Chen <xiaoguang.chen@intel.com>,
        Kirti Wankhede <kwankhede@nvidia.com>,
        Paolo Bonzini <pbonzini@redhat.com>
To: Jike Song <jike.song@intel.com>,
        Alex Williamson <alex.williamson@redhat.com>
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On 10/19/2016 10:32 AM, Jike Song wrote:
+EXPORT_SYMBOL_GPL(vfio_group_set_usrdata);
>>> +
>>> +void *vfio_group_get_usrdata(struct vfio_group *group)
>>> +{
>>> +	return group->usrdata;
>>> +}
>>> +EXPORT_SYMBOL_GPL(vfio_group_get_usrdata);
>>> +
>>> +void *vfio_group_get_usrdata_by_device(struct device *dev)
>>> +{
>>> +	struct vfio_group *vfio_group;
>>> +
>>> +	vfio_group = __vfio_group_get_from_iommu(dev->iommu_group);
>>
>> We actually need to use iommu_group_get() here.  Kirti adds a
>> vfio_group_get_from_dev() in v9 03/12 that does this properly.
>>
>>> +	if (!vfio_group)
>>> +		return NULL;
>>> +
>>> +	return vfio_group_get_usrdata(vfio_group);

I am worrying if the kvm instance got from group->usrdata is safe
enough? What happens if you get the instance after kvm released
kvm-vfio device?