On 03/01/2018 11:36, Thomas Gleixner wrote: > On Wed, 3 Jan 2018, Guillaume Tucker wrote: >> On 03/01/18 09:48, Thomas Gleixner wrote: >>>> Well, it turns out this is not exactly a conflict as there's a >>>> subtle difference between the qemu devices in lab-mhart and in >>>> lab-collabora. The ones in lab-collabora are configured to use >>>> KVM, and it looks like the ones in lab-mhart aren't. >>>> >>>> So this job with KVM enabled passes in lab-collabora: >>>> >>>> https://lava.collabora.co.uk/scheduler/job/1032358 >>>> >>>> but it fails if I tell LAVA (qemu) to disable KVM: >>>> >>>> https://lava.collabora.co.uk/scheduler/job/1032359 >>>> >>>> with the same panic as in lab-mhart. It seems like it's failing >>>> to return from an interrupt: >>>> >>>> http://lava.streamtester.net/scheduler/job/87308 >>>> >>>> [ 2.678828] ? native_iret+0x7/0x7 >>>> [ 2.679208] WARNING: can't dereference iret registers at >>>> 00000000ffc66068 >>>> for ip page_fault+0x11/0x60 >>>> >>>> This triggered an automated bisection on kernelci.org, please see >>>> the results below. >>>> >>>> I may run another bisection with this config enabled earlier in >>>> the history to track down the actual change in the code that >>>> introduced the issue, let me know if it's worth doing. >>> >>> No, because before that commit not all pieces are in place. >>> >>> Can you please try the failing kernel with pti=off on the command line? >> >> It does boot with pti=off (and KVM disabled): >> >> https://lava.collabora.co.uk/scheduler/job/1032387 > > So it's a qemu issue. Added qemu folks on Cc. Reproduced, thanks. I will look into it. Paolo