Subject: [PATCH 14/18] powerpc: move NMI entry/exit code into wrapper

From: Nicholas Piggin <[email-masked]>
Date: Fri, 6 Nov 2020 00:34:27 +1000

This moves the common NMI entry and exit code into the interrupt handler
wrappers.

This changes the behaviour of soft-NMI (watchdog) and HMI interrupts, and
also MCE interrupts on 64e, by adding missing parts of the NMI entry to
them. It fixes a bug with sreset on pseries HPT guests which shouldn't
call nmi_enter().

Signed-off-by: Nicholas Piggin <[email-masked]>
---
 arch/powerpc/include/asm/interrupt.h | 24 ++++++++++++++++++
 arch/powerpc/kernel/mce.c            | 11 --------
 arch/powerpc/kernel/traps.c          | 38 +++++-----------------------
 arch/powerpc/kernel/watchdog.c       | 10 +++-----
 4 files changed, 35 insertions(+), 48 deletions(-)

diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
index 9bd14c59dc8e..a87284707f09 100644
--- a/arch/powerpc/include/asm/interrupt.h
+++ b/arch/powerpc/include/asm/interrupt.h
@@ -69,14 +69,38 @@ static inline void interrupt_async_exit_prepare(struct pt_regs *regs, struct int
 }
 
 struct interrupt_nmi_state {
+#ifdef CONFIG_PPC64
+	u8 ftrace_enabled;
+#endif
 };
 
 static inline void interrupt_nmi_enter_prepare(struct pt_regs *regs, struct interrupt_nmi_state *state)
 {
+#ifdef CONFIG_PPC64
+	state->ftrace_enabled = this_cpu_get_ftrace_enabled();
+	this_cpu_set_ftrace_enabled(0);
+#endif
+
+	/*
+	 * Do not use nmi_enter() for pseries hash guest taking a real-mode
+	 * NMI because not everything it touches is within the RMA limit.
+	 */
+	if (!IS_ENABLED(CONFIG_PPC_BOOK3S_64) ||
+			!firmware_has_feature(FW_FEATURE_LPAR) ||
+			radix_enabled() || (mfmsr() & MSR_DR))
+		nmi_enter();
 }
 
 static inline void interrupt_nmi_exit_prepare(struct pt_regs *regs, struct interrupt_nmi_state *state)
 {
+	if (!IS_ENABLED(CONFIG_PPC_BOOK3S_64) ||
+			!firmware_has_feature(FW_FEATURE_LPAR) ||
+			radix_enabled() || (mfmsr() & MSR_DR))
+		nmi_exit();
+
+#ifdef CONFIG_PPC64
+	this_cpu_set_ftrace_enabled(state->ftrace_enabled);
+#endif
 }
 
 /**
diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
index b84459f45b1a..9f39deed4fca 100644
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -592,12 +592,6 @@ EXPORT_SYMBOL_GPL(machine_check_print_event_info);
 DEFINE_INTERRUPT_HANDLER_NMI(machine_check_early)
 {
 	long handled = 0;
-	u8 ftrace_enabled = this_cpu_get_ftrace_enabled();
-
-	this_cpu_set_ftrace_enabled(0);
-	/* Do not use nmi_enter/exit for pseries hpte guest */
-	if (radix_enabled() || !firmware_has_feature(FW_FEATURE_LPAR))
-		nmi_enter();
 
 	hv_nmi_check_nonrecoverable(regs);
 
@@ -607,11 +601,6 @@ DEFINE_INTERRUPT_HANDLER_NMI(machine_check_early)
 	if (ppc_md.machine_check_early)
 		handled = ppc_md.machine_check_early(regs);
 
-	if (radix_enabled() || !firmware_has_feature(FW_FEATURE_LPAR))
-		nmi_exit();
-
-	this_cpu_set_ftrace_enabled(ftrace_enabled);
-
 	return handled;
 }
 
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 09780481e1b1..95f84c542523 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -443,11 +443,6 @@ DEFINE_INTERRUPT_HANDLER_NMI(system_reset_exception)
 {
 	unsigned long hsrr0, hsrr1;
 	bool saved_hsrrs = false;
-	u8 ftrace_enabled = this_cpu_get_ftrace_enabled();
-
-	this_cpu_set_ftrace_enabled(0);
-
-	nmi_enter();
 
 	/*
 	 * System reset can interrupt code where HSRRs are live and MSR[RI]=1.
@@ -519,10 +514,6 @@ DEFINE_INTERRUPT_HANDLER_NMI(system_reset_exception)
 		mtspr(SPRN_HSRR1, hsrr1);
 	}
 
-	nmi_exit();
-
-	this_cpu_set_ftrace_enabled(ftrace_enabled);
-
 	/* What should we do here? We could issue a shutdown or hard reset. */
 
 	return 0;
@@ -824,6 +815,12 @@ int machine_check_generic(struct pt_regs *regs)
 #endif /* everything else */

+/*
+ * BOOK3S_64 does not call this handler as a non-maskable interrupt
+ * (it uses its own early real-mode handler to handle the MCE proper
+ * and then raises irq_work to call this handler when interrupts are
+ * enabled).
+ */
 #ifdef CONFIG_PPC_BOOK3S_64
 DEFINE_INTERRUPT_HANDLER_ASYNC(machine_check_exception)
 #else
@@ -832,20 +829,6 @@ DEFINE_INTERRUPT_HANDLER_NMI(machine_check_exception)
 {
 	int recover = 0;
 
-	/*
-	 * BOOK3S_64 does not call this handler as a non-maskable interrupt
-	 * (it uses its own early real-mode handler to handle the MCE proper
-	 * and then raises irq_work to call this handler when interrupts are
-	 * enabled).
-	 *
-	 * This is silly. The BOOK3S_64 should just call a different function
-	 * rather than expecting semantics to magically change. Something
-	 * like 'non_nmi_machine_check_exception()', perhaps?
-	 */
-	const bool nmi = !IS_ENABLED(CONFIG_PPC_BOOK3S_64);
-
-	if (nmi) nmi_enter();
-
 	__this_cpu_inc(irq_stat.mce_exceptions);
 
 	add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE);
@@ -870,24 +853,17 @@ DEFINE_INTERRUPT_HANDLER_NMI(machine_check_exception)
 	if (check_io_access(regs))
 		goto bail;
 
-	if (nmi) nmi_exit();
-
 	die("Machine check", regs, SIGBUS);
 
 	/* Must die if the interrupt is not recoverable */
 	if (!(regs->msr & MSR_RI))
 		die("Unrecoverable Machine check", regs, SIGBUS);
 
-#ifdef CONFIG_PPC_BOOK3S_64
 bail:
+#ifdef CONFIG_PPC_BOOK3S_64
 	return;
 #else
 	return 0;
-
-bail:
-	if (nmi) nmi_exit();
-
-	return 0;
 #endif
 }
 
diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
index 824b9376ac35..dc39534836a3 100644
--- a/arch/powerpc/kernel/watchdog.c
+++ b/arch/powerpc/kernel/watchdog.c
@@ -254,11 +254,12 @@ DEFINE_INTERRUPT_HANDLER_NMI(soft_nmi_interrupt)
 	int cpu = raw_smp_processor_id();
 	u64 tb;
 
+	/* should only arrive from kernel, with irqs disabled */
+	WARN_ON_ONCE(!arch_irq_disabled_regs(regs));
+
 	if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
 		return 0;
 
-	nmi_enter();
-
 	__this_cpu_inc(irq_stat.soft_nmi_irqs);
 
 	tb = get_tb();
@@ -266,7 +267,7 @@ DEFINE_INTERRUPT_HANDLER_NMI(soft_nmi_interrupt)
 		wd_smp_lock(&flags);
 		if (cpumask_test_cpu(cpu, &wd_smp_cpus_stuck)) {
 			wd_smp_unlock(&flags);
-			goto out;
+			return 0;
 		}
 		set_cpu_stuck(cpu, tb);
 
@@ -290,9 +291,6 @@ DEFINE_INTERRUPT_HANDLER_NMI(soft_nmi_interrupt)
 	if (wd_panic_timeout_tb < 0x7fffffff)
 		mtspr(SPRN_DEC, wd_panic_timeout_tb);
 
-out:
-	nmi_exit();
-
 	return 0;
 }
 
-- 
2.23.0