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Subject[PATCH 4.4 54/78] cpuidle: powernv: Pass correct drv->cpumask for registration
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>


[ Upstream commit 293d264f13cbde328d5477f49e3103edbc1dc191 ]

drv->cpumask defaults to cpu_possible_mask in __cpuidle_driver_init().
On PowerNV platform cpu_present could be less than cpu_possible in cases
where firmware detects the cpu, but it is not available to the OS. When
CONFIG_HOTPLUG_CPU=n, such cpus are not hotplugable at runtime and hence
we skip creating cpu_device.

This breaks cpuidle on powernv where register_cpu() is not called for
cpus in cpu_possible_mask that cannot be hot-added at runtime.

Trying cpuidle_register_device() on cpu without cpu_device will cause
crash like this:

cpu 0xf: Vector: 380 (Data SLB Access) at [c000000ff1503490]
pc: c00000000022c8bc: string+0x34/0x60
lr: c00000000022ed78: vsnprintf+0x284/0x42c
sp: c000000ff1503710
msr: 9000000000009033
dar: 6000000060000000
current = 0xc000000ff1480000
paca = 0xc00000000fe82d00 softe: 0 irq_happened: 0x01
pid = 1, comm = swapper/8
Linux version 4.11.0-rc2 (sv@sagarika) (gcc version 4.9.4
(Buildroot 2017.02-00004-gc28573e) ) #15 SMP Fri Mar 17 19:32:02 IST 2017
enter ? for help
[link register ] c00000000022ed78 vsnprintf+0x284/0x42c
[c000000ff1503710] c00000000022ebb8 vsnprintf+0xc4/0x42c (unreliable)
[c000000ff1503800] c00000000022ef40 vscnprintf+0x20/0x44
[c000000ff1503830] c0000000000ab61c vprintk_emit+0x94/0x2cc
[c000000ff15038a0] c0000000000acc9c vprintk_func+0x60/0x74
[c000000ff15038c0] c000000000619694 printk+0x38/0x4c
[c000000ff15038e0] c000000000224950 kobject_get+0x40/0x60
[c000000ff1503950] c00000000022507c kobject_add_internal+0x60/0x2c4
[c000000ff15039e0] c000000000225350 kobject_init_and_add+0x70/0x78
[c000000ff1503a60] c00000000053c288 cpuidle_add_sysfs+0x9c/0xe0
[c000000ff1503ae0] c00000000053aeac cpuidle_register_device+0xd4/0x12c
[c000000ff1503b30] c00000000053b108 cpuidle_register+0x98/0xcc
[c000000ff1503bc0] c00000000085eaf0 powernv_processor_idle_init+0x140/0x1e0
[c000000ff1503c60] c00000000000cd60 do_one_initcall+0xc0/0x15c
[c000000ff1503d20] c000000000833e84 kernel_init_freeable+0x1a0/0x25c
[c000000ff1503dc0] c00000000000d478 kernel_init+0x24/0x12c
[c000000ff1503e30] c00000000000b564 ret_from_kernel_thread+0x5c/0x78

This patch fixes the bug by passing correct cpumask from
powernv-cpuidle driver.

Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
[ rjw: Comment massage ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/cpuidle/cpuidle-powernv.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)

--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c
@@ -160,6 +160,24 @@ static int powernv_cpuidle_driver_init(v
drv->state_count += 1;
}

+ /*
+ * On the PowerNV platform cpu_present may be less than cpu_possible in
+ * cases when firmware detects the CPU, but it is not available to the
+ * OS. If CONFIG_HOTPLUG_CPU=n, then such CPUs are not hotplugable at
+ * run time and hence cpu_devices are not created for those CPUs by the
+ * generic topology_init().
+ *
+ * drv->cpumask defaults to cpu_possible_mask in
+ * __cpuidle_driver_init(). This breaks cpuidle on PowerNV where
+ * cpu_devices are not created for CPUs in cpu_possible_mask that
+ * cannot be hot-added later at run time.
+ *
+ * Trying cpuidle_register_device() on a CPU without a cpu_device is
+ * incorrect, so pass a correct CPU mask to the generic cpuidle driver.
+ */
+
+ drv->cpumask = (struct cpumask *)cpu_present_mask;
+
return 0;
}


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