The hardware can execute stop in any context, and KVM does not
require real mode because siblings do not share MMU state. This
saves a switch to real-mode when going idle.
Acked-by: Gautham R. Shenoy <e...@linux.vnet.ibm.com>
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
arch/powerpc/kernel/idle_book3s.S | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/arch/powerpc/kernel/idle_book3s.S
b/arch/powerpc/kernel/idle_book3s.S
index 3b701b1a5e87..fc5145339277 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -141,7 +141,16 @@ pnv_powersave_common:
std r5,_CCR(r1)
std r1,PACAR1(r13)
+BEGIN_FTR_SECTION
+ /*
+ * POWER9 does not require real mode to stop, and does not set
+ * hwthread_state for KVM (threads don't share MMU context), so
+ * we can remain in virtual mode for this.
+ */
+ bctr
+END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
/*
+ * POWER8
* Go to real mode to do the nap, as required by the architecture.
* Also, we need to be in real mode before setting hwthread_state,
* because as soon as we do that, another thread can switch
--
2.13.3
