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

From: Zhou Jie <zhoujie2011@cn.fujitsu.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: Chen Fan <fan.chen@easystack.cn>,
	Chen Fan <chen.fan.fnst@cn.fujitsu.com>,
	izumi.taku@jp.fujitsu.com, caoj.fnst@cn.fujitsu.com,
	qemu-devel@nongnu.org, mst@redhat.com
Subject: Re: [Qemu-devel] [PATCH v8 11/12] vfio: register aer resume notification handler for aer resume
Date: Wed, 22 Jun 2016 13:45:10 +0800	[thread overview]
Message-ID: <113474d2-8408-db49-e7ef-8c6b736af866@cn.fujitsu.com> (raw)
In-Reply-To: <20160621215626.71c99582@t450s.home>

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.

Sincerely
Zhoujie