linux-kernel - [PATCH 4.17 051/220] powerpc/powernv/cpuidle: Init all present cpus for deep states

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Message-Id: <20180701160910.457887906@linuxfoundation.org>
Date:   Sun,  1 Jul 2018 18:21:15 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Akshay Adiga <akshay.adiga@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.17 051/220] powerpc/powernv/cpuidle: Init all present cpus for deep states

4.17-stable review patch.  If anyone has any objections, please let me know.

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

From: Akshay Adiga <akshay.adiga@...ux.vnet.ibm.com>

commit ac9816dcbab53c57bcf1d7b15370b08f1e284318 upstream.

Init all present cpus for deep states instead of "all possible" cpus.
Init fails if a possible cpu is guarded. Resulting in making only
non-deep states available for cpuidle/hotplug.

Stewart says, this means that for single threaded workloads, if you
guard out a CPU core you'll not get WoF (Workload Optimised
Frequency), which means that performance goes down when you wouldn't
expect it to.

Fixes: 77b54e9f213f ("powernv/powerpc: Add winkle support for offline cpus")
Cc: stable@...r.kernel.org # v3.19+
Signed-off-by: Akshay Adiga <akshay.adiga@...ux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/platforms/powernv/idle.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/powerpc/platforms/powernv/idle.c
+++ b/arch/powerpc/platforms/powernv/idle.c
@@ -79,7 +79,7 @@ static int pnv_save_sprs_for_deep_states
 	uint64_t msr_val = MSR_IDLE;
 	uint64_t psscr_val = pnv_deepest_stop_psscr_val;
 
-	for_each_possible_cpu(cpu) {
+	for_each_present_cpu(cpu) {
 		uint64_t pir = get_hard_smp_processor_id(cpu);
 		uint64_t hsprg0_val = (uint64_t)paca_ptrs[cpu];
 
@@ -814,7 +814,7 @@ static int __init pnv_init_idle_states(v
 		int cpu;
 
 		pr_info("powernv: idle: Saving PACA pointers of all CPUs in their thread sibling PACA\n");
-		for_each_possible_cpu(cpu) {
+		for_each_present_cpu(cpu) {
 			int base_cpu = cpu_first_thread_sibling(cpu);
 			int idx = cpu_thread_in_core(cpu);
 			int i;