linux-kernel - Fwd: Cpu hotplug causes stutter on AMD platform, how can I disable it?

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Date:	Sun, 24 Feb 2013 22:59:13 +0100
From:	Mario Giammarco <mgiammarco@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Fwd: Cpu hotplug causes stutter on AMD platform, how can I disable it?

Hello,
I have an AMD Athlon(tm) II X4 635 Processor
on an asus M4A89TD PRO/USB3   motherboard with AMD 890FX chipset.
When I play videos on nvidia card (even on open source driver) the
video stutters and I can
see in syslog:

Feb 24 00:30:50 virtual1 kernel: [  719.834878] CPU 1 is now offline
Feb 24 00:30:50 virtual1 kernel: [  719.842450] CPU 2 is now offline
Feb 24 00:30:50 virtual1 kernel: [  719.852534] CPU 3 is now offline
Feb 24 00:30:50 virtual1 kernel: [  719.852538] SMP alternatives:
switching to UP code
Feb 24 00:30:51 virtual1 /usr/sbin/irqbalance: WARNING, didn't collect
load info for all cpus, balancing is broken
Feb 24 00:30:52 virtual1 kernel: [  722.294565] SMP alternatives:
switching to SMP code
Feb 24 00:30:52 virtual1 kernel: [  722.334866] Booting Node 0
Processor 1 APIC 0x1
Feb 24 00:30:52 virtual1 kernel: [  722.346033] LVT offset 1 assigned
for vector 0x400
Feb 24 00:30:52 virtual1 kernel: [  722.361174] Switch to broadcast mode on CPU1
Feb 24 00:30:52 virtual1 kernel: [  722.378717] microcode: CPU1: new
patch_level=0x010000db
Feb 24 00:30:52 virtual1 kernel: [  722.398515] Booting Node 0
Processor 2 APIC 0x2
Feb 24 00:30:52 virtual1 kernel: [  722.413375] Switch to broadcast mode on CPU2
Feb 24 00:30:52 virtual1 kernel: [  722.420603] microcode: CPU2: new
patch_level=0x010000db
Feb 24 00:30:52 virtual1 kernel: [  722.428782] Booting Node 0
Processor 3 APIC 0x3
Feb 24 00:30:52 virtual1 kernel: [  722.446283] Switch to broadcast mode on CPU3
Feb 24 00:30:52 virtual1 kernel: [  722.448615] microcode: CPU3: new
patch_level=0x010000db

I have searched on internet and I see that is a problem common to
several AMD platforms.
Even in Microsoft Windows several people have the same problem and
they solved it disabling cool&quiet on bios. It seems that some amd
cpus on power saving cut off also HT bus blocking data from pcie bus
(!?!)
I have tried too and infact disabling cool&quiet improves a lot the problem.
But I would like to find a better solution, can I disable cpu hotplug?
Have you heard of this bug before?
Please CC me because I am not on kernel mailing list.

Thanks in advance for any help,
Mario
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