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

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Date:   Tue, 6 Jun 2017 15:39:59 +0200
From:   Max Vozeler <max@...terhof.net>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        "Charles (Chas) Williams" <ciwillia@...cade.com>,
        "M. Vefa Bicakci" <m.v.b@...box.com>,
        Alok Kataria <akataria@...are.com>,
        xen-devel <xen-devel@...ts.xen.org>,
        Juergen Groß <jgross@...e.com>,
        Thomas Weißschuh <kernel@...ssschuh.net>
Subject: Re: [PATCH v2] x86/smpboot: Make logical package management more
 robust

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                          

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)

Any ideas? 

Thanks and kind regards,

	Max 

View attachment "bisect.log" of type "text/plain" (2010 bytes)

View attachment "dmesg-ok.txt" of type "text/plain" (17746 bytes)