[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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

From: Zhou Jie
Subject: Re: [Qemu-devel] [PATCH v8 11/12] vfio: register aer resume notification handler for aer resume
Date: Tue, 21 Jun 2016 10:16:25 +0800
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.1.0

Hi, Alex

I was really hoping to hear your opinion, or at least some further
discussion of pros and cons rather than simply parroting back my idea.
I understand.

My current thinking is that a resume notifier to userspace is poorly
defined, it's not clear what the user can and cannot do between an
error notification and the resume notification.
Yes, do nothing between that time is better.

One approach to solve
that might be that the kernel internally handles the resume
notifications.  Maybe that means blocking the ioctl (interruptible
timeout) until the internal resume occurs, or maybe that means
returning -EAGAIN.
I don't think it is a good idea.
The kernel give the error and resume notifications, it's enough.
It's up to user to how to use them.

Probably implementations of each need to be worked
through to determine which is better.  We don't want to add complexity
to the kernel simply to make things easier for userspace, but we also
don't want a poorly specified interface that is difficult for
userspace to use correctly.  Thanks,
In qemu, the aer recovery process:
  1. Detect support for resume notification
     If host vfio driver does not support for resume notification,
     directly fail to boot up VM as with aer enabled.
  2. Immediately notify the VM on error detected.
  3. Disable the device.
     Unmap the config space and bar region.
  4. Delay the guest directed bus reset.
  5. Wait for resume notification.
     If we don't get the resume notification from the host after
     some timeout, we would abort the guest directed bus reset
     altogether and unplug of the device to prevent it from further
     interacting with the VM.
  6. After get the resume notification reset bus and enable the device.

I think we only make sure the disabled device
 will not interact with the VM.

Zhou jie



Dept 1
No. 6 Wenzhu Road,
Nanjing, 210012, China

reply via email to

[Prev in Thread] Current Thread [Next in Thread]