powerpc/64e: remove implicit soft-masking and interrupt exit restart logic

The implicit soft-masking to speed up interrupt return was going to be
used by 64e as well, but it has not been extensively tested on that
platform and is not considered ready. It was intended to be disabled
before merge. Disable it for now.

Most of the restart code is common with 64s, so with more correctness
and performance testing this could be re-enabled again by adding the
extra soft-mask checks to interrupt handlers and flipping
exit_must_hard_disable().

Fixes: 9d1988ca87dd ("powerpc/64: treat low kernel text as irqs soft-masked")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210630074621.2109197-4-npiggin@gmail.com

1 files changed, 24 insertions, 9 deletions

diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
index 8b4b1e84e110..f13c93b033c7 100644
--- a/arch/powerpc/include/asm/interrupt.h
+++ b/arch/powerpc/include/asm/interrupt.h
@@ -73,20 +73,34 @@
 #include <asm/kprobes.h>
 #include <asm/runlatch.h>
 
-#ifdef CONFIG_PPC64
+#ifdef CONFIG_PPC_BOOK3S_64
 extern char __end_soft_masked[];
 unsigned long search_kernel_restart_table(unsigned long addr);
-#endif
 
-#ifdef CONFIG_PPC_BOOK3S_64
 DECLARE_STATIC_KEY_FALSE(interrupt_exit_not_reentrant);
 
+static inline bool is_implicit_soft_masked(struct pt_regs *regs)
+{
+	if (regs->msr & MSR_PR)
+		return false;
+
+	if (regs->nip >= (unsigned long)__end_soft_masked)
+		return false;
+
+	return true;
+}
+
 static inline void srr_regs_clobbered(void)
 {
 	local_paca->srr_valid = 0;
 	local_paca->hsrr_valid = 0;
 }
 #else
+static inline bool is_implicit_soft_masked(struct pt_regs *regs)
+{
+	return false;
+}
+
 static inline void srr_regs_clobbered(void)
 {
 }
@@ -150,11 +164,13 @@ static inline void interrupt_enter_prepare(struct pt_regs *regs, struct interrup
 		 */
 		if (TRAP(regs) != INTERRUPT_PROGRAM) {
 			CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
-			BUG_ON(regs->nip < (unsigned long)__end_soft_masked);
+			BUG_ON(is_implicit_soft_masked(regs));
 		}
+#ifdef CONFIG_PPC_BOOK3S
 		/* Move this under a debugging check */
 		if (arch_irq_disabled_regs(regs))
 			BUG_ON(search_kernel_restart_table(regs->nip));
+#endif
 	}
 #endif
 
@@ -244,10 +260,9 @@ static inline void interrupt_nmi_enter_prepare(struct pt_regs *regs, struct inte
 	local_paca->irq_soft_mask = IRQS_ALL_DISABLED;
 	local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
 
-	if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && !(regs->msr & MSR_PR) &&
-				regs->nip < (unsigned long)__end_soft_masked) {
-		// Kernel code running below __end_soft_masked is
-		// implicitly soft-masked.
+	if (is_implicit_soft_masked(regs)) {
+		// Adjust regs->softe soft implicit soft-mask, so
+		// arch_irq_disabled_regs(regs) behaves as expected.
 		regs->softe = IRQS_ALL_DISABLED;
 	}
 
@@ -282,6 +297,7 @@ static inline void interrupt_nmi_exit_prepare(struct pt_regs *regs, struct inter
 	 */
 
 #ifdef CONFIG_PPC64
+#ifdef CONFIG_PPC_BOOK3S
 	if (arch_irq_disabled_regs(regs)) {
 		unsigned long rst = search_kernel_restart_table(regs->nip);
 		if (rst)
@@ -289,7 +305,6 @@ static inline void interrupt_nmi_exit_prepare(struct pt_regs *regs, struct inter
 	}
 #endif
 
-#ifdef CONFIG_PPC64
 	if (nmi_disables_ftrace(regs))
 		this_cpu_set_ftrace_enabled(state->ftrace_enabled);