Commit 4387e9ff25 ("[POWERPC] Fix PMU + soft interrupt disable bug")
hard disabled interrupts over the low level context switch, because
the SLB management can't cope with a PMU interrupt accesing the stack
in that window.
Radix based kernel mapping does not use the SLB so it does not require
interrupts disabled here. This is worth 1-2% in context switch
performance.
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
arch/powerpc/kernel/process.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 633ec9967141..ea1618b62bf8 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1199,12 +1199,14 @@ struct task_struct *__switch_to(struct task_struct
*prev,
__switch_to_tm(prev, new);
- /*
- * We can't take a PMU exception inside _switch() since there is a
- * window where the kernel stack SLB and the kernel stack are out
- * of sync. Hard disable here.
- */
- hard_irq_disable();
+ if (!radix_enabled()) {
+ /*
+ * We can't take a PMU exception inside _switch() since there
+ * is a window where the kernel stack SLB and the kernel stack
+ * are out of sync. Hard disable here.
+ */
+ hard_irq_disable();
+ }
/*
* Call restore_sprs() before calling _switch(). If we move it after
--
2.11.0
