kernel bug in "Drop WIMG in favour of new constants"?

[Aneesh Kumar K.V]

"Aneesh Kumar K.V" <aneesh.kumar at linux.vnet.ibm.com> writes:

> "Darrick J. Wong" <darrick.wong at oracle.com> writes:
>
>> On Thu, Jun 16, 2016 at 03:23:47PM +1000, Michael Ellerman wrote:
>>> On Wed, 2016-06-15 at 21:33 -0700, Darrick J. Wong wrote:
>>> 
>>> > Hi Aneesh,
>>> > 
>>> > I noticed when trying out 4.7-rc3 on qemu-2.5 that the kernel no longer
>>> > boots.  4.6 booted just fine, so I bisected the kernel to the commit
>>> > 30bda41aba4efb2370c97e2cbe7385de93ccc372, which is "powerpc/mm: Drop WIMG in
>>> > favour of new constants".  The changelog suggests that the KVM changes need
>>> > closer review, and here's an actual crash:
>>> > 
>>> > (I can send libvirt's machine xml, .config, and full dmesg if that helps.)
>>> 
>>> Yes please.
>>> 
>>> I'm successfully booting 4.7-rc's on qemu (2.5.0 (Debian 1:2.5+dfsg-5ubuntu10.1)).
>>
>> Ok, see attached.  I also sent along the dpkg --status output for qemu
>> and qemu-slof; looks like we're running the same Ubuntu packages...
>>
>> ...my host kernel is 4.6.0 on x64.
>
> So this is Qemu TCG mode right ? I will try some test and update later.
>

I am able to reproduce this with

qemu-system-ppc64 -kernel vmlinux -machine
type=pseries,usb=off -smp 1 -m 1G  -vga none -nographic    -device
usb-ehci -device usb-kbd -device usb-mouse

Looks like enabling usb device is the issue.

-aneesh