Re: [PATCH 1/2] KVM: page track: add a new notifier type: track_flush_slot

[Xiao Guangrong <guangrong.xiao@linux.intel.com>]

On 10/11/2016 04:54 PM, Paolo Bonzini wrote:
>
>
> On 11/10/2016 04:39, Xiao Guangrong wrote:
>>
>>
>> On 10/11/2016 02:32 AM, Paolo Bonzini wrote:
>>>
>>>
>>> On 10/10/2016 20:01, Neo Jia wrote:
>>>>> Hi Neo,
>>>>>
>>>>> AFAIK this is needed because KVMGT doesn't paravirtualize the PPGTT,
>>>>> while nVidia does.
>>>>
>>>> Hi Paolo and Xiaoguang,
>>>>
>>>> I am just wondering how device driver can register a notifier so he
>>>> can be
>>>> notified for write-protected pages when writes are happening.
>>>
>>> It can't yet, but the API is ready for that.  kvm_vfio_set_group is
>>> currently where a struct kvm_device* and struct vfio_group* touch. Given
>>> a struct kvm_device*, dev->kvm provides the struct kvm to be passed to
>>> kvm_page_track_register_notifier.  So I guess you could add a callback
>>> that passes the struct kvm_device* to the mdev device.
>>>
>>> Xiaoguang and Guangrong, what were your plans?  We discussed it briefly
>>> at KVM Forum but I don't remember the details.
>>>
>>
>> Your suggestion was that pass kvm fd to KVMGT via VFIO, so that we can
>> figure out the kvm instance based on the fd.
>>
>> We got a new idea, how about search the kvm instance by mm_struct, it
>> can work as KVMGT is running in the vcpu context and it is much more
>> straightforward.
>
> Perhaps I didn't understand your suggestion, but the same mm_struct can
> have more than 1 struct kvm so I'm not sure that it can work.

vcpu->pid is valid during vcpu running so that it can be used to figure
out which kvm instance owns the vcpu whose pid is the one as current
thread, i think it can work. :)