[vbox-dev] Kernel API changes for kernel 4.10

Larry Finger Larry.Finger at lwfinger.net
Fri Jan 6 17:06:19 UTC 2017

On 01/06/2017 08:06 AM, Frank Mehnert wrote:
> Hi Larry,
> On Dienstag, 3. Januar 2017 21:48:06 CET Larry Finger wrote:
>> On 12/27/2016 11:16 AM, Larry Finger wrote:
>>> On 12/27/2016 10:56 AM, Larry Finger wrote:
>>>> In kernel 4.10-rc1, the kernel routines register_cpu_notifier() and
>>>> unregister_cpu_notifier() have been removed and their function replaced by
>>>> callbacks from the hotplug state machine. After looking at the changes required
>>>> in some other drivers, I have seen that the required changes will not be
>>>> trivial. Before I start doing the work, I want to know if the changes have been
>>>> started and/or done by Oracle.
>>> One thing I failed to mention. Commit 7fd8329ba502 in 4.10-rc1 also messes up
>>> the ability to define true/false in an out-of-kernel driver. I have submitted a
>>> kernel patch to fix this
>>> (http://lkml.iu.edu/hypermail/linux/kernel/1612.3/00086.html), but it has not
>>> yet been merged or received any comments.
>> My patch was merged today. It has not yet hit mainline, but I expect it to be
>> there as of 4.10-rc3. I still have no fix for the missing
>> register_cpu_notifier(), etc.
> thanks for the information. I assume we will do it like the Linux kernel and use
> cpuhp_setup_state_nocalls() to register CPU hotplug callbacks. But before we can
> provide a fix we need to do a few tests.

I think that is the correct approach, but I have not had time to actually do it 
yet. Unlike most API changes, this one is a bit more intrusive. Once you get a 
patch, I would be pleased to help test it. Having to boot an old kernel to run a 
VM is getting old. In addition, the openSUSE kernel HEAD project is running 
4.10-rcX kernels, and the VB build fails every time they trigger a new build.



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