[PATCH 2/2] UBUNTU: SAUCE: powerpc/powernv/cpuidle: Pass correct drv->cpumask for registration

[Tim Gardner]

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

BugLink: http://bugs.launchpad.net/bugs/1674325

http://patchwork.ozlabs.org/patch/740414/

drv->cpumask defaults to cpu_possible_mask in __cpuidle_driver_init().
This breaks cpuidle on powernv where sysfs files are not created for
cpus in cpu_possible_mask that cannot be hot-added.

Trying cpuidle_register_device() on cpu without sysfs node will
cause crash like:

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 at 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 issue by passing correct cpumask from
powernv-cpuidle driver.

Signed-off-by: Vaidyanathan Srinivasan <svaidy at linux.vnet.ibm.com>
Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
---
 drivers/cpuidle/cpuidle-powernv.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index 9283d41..3d87231 100644
--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c
@@ -185,6 +185,28 @@ static int powernv_cpuidle_driver_init(void)
 		drv->state_count += 1;
 	}
 
+	/*
+	 * On PowerNV platform cpu_present may be less that cpu_possible
+	 * in cases where firmware detects the cpu, but it is not available
+	 * for OS.  Such CPUs are not hotplugable at runtime on PowerNV
+	 * platform and hence sysfs files are not created for those.
+	 * Generic topology_init() would skip creating sysfs directories
+	 * for cpus that are not present and not hotplugable later at
+	 * runtime.
+	 *
+	 * drv->cpumask defaults to cpu_possible_mask in __cpuidle_driver_init().
+	 * This breaks cpuidle on powernv where sysfs files are not created for
+	 * cpus in cpu_possible_mask that cannot be hot-added.
+	 *
+	 * Hence at runtime sysfs nodes are present for cpus only in
+	 * cpu_present_mask. Trying cpuidle_register_device() on cpu without
+	 * sysfs node is incorrect.
+	 *
+	 * Hence pass correct cpu mask to generic cpuidle driver.
+	 */
+
+	drv->cpumask = (struct cpumask *)cpu_present_mask;
+
 	return 0;
 }
 
-- 
2.7.4