On 2015年11月25日 13:30, Alexander Duyck wrote:

No, what I am getting at is that you can't go around and modify the
configuration space for every possible device out there.  This
solution won't scale.

PCI config space regs are emulation by Qemu and so We can find the free
PCI config space regs for the faked PCI capability. Its position can be
not permanent.

 If you instead moved the logic for notifying
the device into a separate mechanism such as making it a part of the
hot-plug logic then you only have to write the code once per OS in
order to get the hot-plug capability to pause/resume the device.  What
I am talking about is not full hot-plug, but rather to extend the
existing hot-plug in Qemu and the Linux kernel to support a
"pause/resume" functionality.  The PCI hot-plug specification calls
out the option of implementing something like this, but we don't
currently have support for it.

Could you elaborate the part of PCI hot-plug specification you mentioned?

My concern is whether it needs to change PCI spec or not.

I just feel doing it through PCI hot-plug messages will scale much
better as you could likely make use of the power management
suspend/resume calls to take care of most of the needed implementation
details.

- Alex

-- 
Best regards
Tianyu Lan