linux-kernel - Re: [PATCH] powerpc: use device_online/offline() instead of cpu

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Date:	Sun, 2 Nov 2014 10:28:51 +0530
From:	Bharata B Rao <bharata@...ux.vnet.ibm.com>
To:	Dan Streetman <ddstreet@...e.org>
Cc:	Nathan Fontenot <nfont@...ux.vnet.ibm.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>,
	Paul Mackerras <paulus@...ba.org>,
	Thomas Falcon <tlfalcon@...ux.vnet.ibm.com>,
	Grant Likely <grant.likely@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Daniel Walter <dwalter@...gle.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Neil Zhang <zhangwm@...vell.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc: use device_online/offline() instead of
 cpu_up/down()

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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