Re: [Qemu-devel] [PATCH v8 11/12] vfio: register aer resume notification handler for aer resume

[Zhou Jie <zhoujie2011@cn.fujitsu.com>]

Hi Alex,

On 2016/6/22 13:45, Zhou Jie wrote:
> Hi Alex,
>
>>>
>>> In vfio I have some questions.
>>> 1. How can I disable the access by mmap?
>>>     We can disable all access to vfio fd by returning a EAGAIN error
>>>     if user try to access it during the reset period until the host
>>>     reset finished.
>>>     But about the bar region which is maped by vfio_pci_mmap.
>>>     How can I disable it in vfio driver?
>>>     Even there is a way to do it,
>>>     how about the complexity to recovery the mmap?
>>
>> That's exactly the "sticky point" I refer to above, you'd need to
>> solve that problem.  MST would probably still argue that we don't need
>> to disable all those interfaces, a userspace driver can already do
>> things like disable mmio space and then attempt to read from the mmio
>> space of the device.
> You said we should not depend on user to protect the device
>  be accessed during the reset period.
>
>> So maybe the problem can be simplified to
>> non-device specific interfaces, like config space access plus ioctls.
> I don't understand what's your mean.

When a fatal aer error occurs the process is following.
For host
    aer driver detect aer error
-> vfio driver send aer error
-> aer driver reset bus
-> qemu report aer error
For guest
-> aer driver detect aer error
-> aer driver reset bus
-> device driver maybe disable device

I am not sure if all the device driver disable device
when a fatal aer error occurs.
Should we depend on the guest device driver to protect the device
be accessed during the reset period?

Sincerely
Zhoujie