From 8c1c7fb0b5ec95c392e9b585a6cf8cde254308d3 Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@gmail.com>
Date: Sat, 18 Nov 2017 00:08:06 +1000
Subject: [PATCH] powerpc/64s/idle: avoid sync for KVM state when waking from
idle
References: bsc#1061840
Patch-mainline: v4.17-rc1
Git-commit: 8c1c7fb0b5ec95c392e9b585a6cf8cde254308d3
When waking from a CPU idle instruction (e.g., nap or stop), the sync
for ordering the KVM secondary thread state can be avoided if there
wakeup is coming from a kernel context rather than KVM context.
This improves performance for ping-pong benchmark with the stop0 idle
state by 0.46% for 2 threads in the same core, and 1.02% for different
cores.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
arch/powerpc/kernel/idle_book3s.S | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index 2896ccf3138d..903ec2a5c76c 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -551,6 +551,9 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_ARCH_300)
mr r3,r12
#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
+ lbz r0,HSTATE_HWTHREAD_STATE(r13)
+ cmpwi r0,KVM_HWTHREAD_IN_KERNEL
+ beq 1f
li r0,KVM_HWTHREAD_IN_KERNEL
stb r0,HSTATE_HWTHREAD_STATE(r13)
/* Order setting hwthread_state vs. testing hwthread_req */
--
2.13.6