Re: [PATCH v2] x86/smpboot: Make logical package management more robust

[Boris Ostrovsky]

On 06/06/2017 09:39 AM, Max Vozeler wrote:
> Hi Thomas,
>
> there is a problem booting recent kernels on some Xen domUs hosted by
> provider JiffyBox.
>
> The kernel seems to crash just after logging
> [    0.038700] SMP alternatives: switching to SMP code


Do you have the crash splat? Stack trace and such.

In fact, full boot log might be useful.

> We started seeing this with 4.9.2 and bisecting the 4.9 stable kernels
> determined that this commit introduced the problem. Reverting it from 4.9.2
> makes the kernel boot again.
>
> Older kernels (starting from 3.16 up to and including 4.9.1) were running
> fine in this setup. But recent mainline (tested 4.12-rc3) and 4.9.x both
> fail to boot there.
>
> Unfortunately we have no detailed information about the hypervisor or
> setup and the provider is not very forthcoming with details. I'm attaching
> dmesg of a successful boot (4.9.2 with this commit reverted).
>
> It shows a fairly old XEN version:
>
> [    0.000000] Xen version: 3.1.2-416.el5 (preserve-AD)


This is a 10 year old hypervisor so it's not especially surprising that 
newer kernels don't work. (If anything, I am surprised that you actually 
booted 4.9 at all).

There have been a bunch of problems in this area (topology) on PV guests.


-boris