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Date: Sun, 2 Nov 2014 10:28:51 +0530
From: Bharata B Rao <bharata@linux.vnet.ibm.com>
To: Dan Streetman <ddstreet@ieee.org>
Cc: Nathan Fontenot <nfont@linux.vnet.ibm.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
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        Neil Zhang <zhangwm@marvell.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] powerpc: use device_online/offline() instead of
 cpu_up/down()
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On Fri, Oct 31, 2014 at 03:41:34PM -0400, Dan Streetman wrote:
> In powerpc pseries platform dlpar operations, Use device_online() and
> device_offline() instead of cpu_up() and cpu_down().
> 
> Calling cpu_up/down directly does not update the cpu device offline
> field, which is used to online/offline a cpu from sysfs.  Calling
> device_online/offline instead keeps the sysfs cpu online value correct.
> The hotplug lock, which is required to be held when calling
> device_online/offline, is already held when dlpar_online/offline_cpu
> are called, since they are called only from cpu_probe|release_store.
> 
> This patch fixes errors on PowerVM systems that have cpu(s) added/removed
> using dlpar operations; without this patch, the
> /sys/devices/system/cpu/cpuN/online nodes do not correctly show the
> online state of added/removed cpus.

Verified the patch to be working as expected when I online and offline
CPUs of a PowerKVM guest using QEMU (plus my RFC hotplug patchset for
QEMU)

Regards,
Bharata.

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