powerpc/64e/interrupt: NMI save irq soft-mask state in C

64e non-maskable interrupts save the state of the irq soft-mask in
asm. This can be done in C in interrupt wrappers as 64s does.

I haven't been able to test this with qemu because it doesn't seem
to cause FSL bookE WDT interrupts.

This makes WatchdogException an NMI interrupt, which affects 32-bit
as well (okay, or create a new handler?)
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210316104206.407354-6-npiggin@gmail.com

arch/powerpc/include/asm/interrupt.h

@@ -149,18 +149,32 @@ static inline void interrupt_async_exit_prepare(struct pt_regs *regs, struct int
 
 struct interrupt_nmi_state {
 #ifdef CONFIG_PPC64
-#ifdef CONFIG_PPC_BOOK3S_64
 	u8 irq_soft_mask;
 	u8 irq_happened;
-#endif
 	u8 ftrace_enabled;
 #endif
 };
 
+static inline bool nmi_disables_ftrace(struct pt_regs *regs)
+{
+	/* Allow DEC and PMI to be traced when they are soft-NMI */
+	if (IS_ENABLED(CONFIG_PPC_BOOK3S_64)) {
+		if (TRAP(regs) == 0x900)
+		       return false;
+		if (TRAP(regs) == 0xf00)
+		       return false;
+	}
+	if (IS_ENABLED(CONFIG_PPC_BOOK3E)) {
+		if (TRAP(regs) == 0x260)
+			return false;
+	}
+
+	return true;
+}
+
 static inline void interrupt_nmi_enter_prepare(struct pt_regs *regs, struct interrupt_nmi_state *state)
 {
 #ifdef CONFIG_PPC64
-#ifdef CONFIG_PPC_BOOK3S_64
 	state->irq_soft_mask = local_paca->irq_soft_mask;
 	state->irq_happened = local_paca->irq_happened;
 
@@ -173,9 +187,8 @@ static inline void interrupt_nmi_enter_prepare(struct pt_regs *regs, struct inte
 	local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
 
 	/* Don't do any per-CPU operations until interrupt state is fixed */
-#endif
-	/* Allow DEC and PMI to be traced when they are soft-NMI */
-	if (TRAP(regs) != 0x900 && TRAP(regs) != 0xf00 && TRAP(regs) != 0x260) {
+
+	if (nmi_disables_ftrace(regs)) {
 		state->ftrace_enabled = this_cpu_get_ftrace_enabled();
 		this_cpu_set_ftrace_enabled(0);
 	}
@@ -204,16 +217,14 @@ static inline void interrupt_nmi_exit_prepare(struct pt_regs *regs, struct inter
 	 */
 
 #ifdef CONFIG_PPC64
-	if (TRAP(regs) != 0x900 && TRAP(regs) != 0xf00 && TRAP(regs) != 0x260)
+	if (nmi_disables_ftrace(regs))
 		this_cpu_set_ftrace_enabled(state->ftrace_enabled);
 
-#ifdef CONFIG_PPC_BOOK3S_64
 	/* Check we didn't change the pending interrupt mask. */
 	WARN_ON_ONCE((state->irq_happened | PACA_IRQ_HARD_DIS) != local_paca->irq_happened);
 	local_paca->irq_happened = state->irq_happened;
 	local_paca->irq_soft_mask = state->irq_soft_mask;
 #endif
-#endif
 }
 
 /*
@@ -426,6 +437,7 @@ DECLARE_INTERRUPT_HANDLER(SMIException);
 DECLARE_INTERRUPT_HANDLER(handle_hmi_exception);
 DECLARE_INTERRUPT_HANDLER(unknown_exception);
 DECLARE_INTERRUPT_HANDLER_ASYNC(unknown_async_exception);
+DECLARE_INTERRUPT_HANDLER_NMI(unknown_nmi_exception);
 DECLARE_INTERRUPT_HANDLER(instruction_breakpoint_exception);
 DECLARE_INTERRUPT_HANDLER(RunModeException);
 DECLARE_INTERRUPT_HANDLER(single_step_exception);
@@ -449,7 +461,7 @@ DECLARE_INTERRUPT_HANDLER(altivec_assist_exception);
 DECLARE_INTERRUPT_HANDLER(CacheLockingException);
 DECLARE_INTERRUPT_HANDLER(SPEFloatingPointException);
 DECLARE_INTERRUPT_HANDLER(SPEFloatingPointRoundException);
-DECLARE_INTERRUPT_HANDLER(WatchdogException);
+DECLARE_INTERRUPT_HANDLER_NMI(WatchdogException);
 DECLARE_INTERRUPT_HANDLER(kernel_bad_stack);
 
 /* slb.c */

arch/powerpc/kernel/exceptions-64e.S

@@ -63,9 +63,6 @@
 	ld	reg, (SPECIAL_EXC_##name * 8 + SPECIAL_EXC_FRAME_OFFS)(r1)
 
 special_reg_save:
-	lbz	r9,PACAIRQHAPPENED(r13)
-	RECONCILE_IRQ_STATE(r3,r4)
-
 	/*
 	 * We only need (or have stack space) to save this stuff if
 	 * we interrupted the kernel.
@@ -119,15 +116,11 @@ BEGIN_FTR_SECTION
 	mtspr	SPRN_MAS5,r10
 	mtspr	SPRN_MAS8,r10
 END_FTR_SECTION_IFSET(CPU_FTR_EMB_HV)
-	SPECIAL_EXC_STORE(r9,IRQHAPPENED)
-
 	mfspr	r10,SPRN_DEAR
 	SPECIAL_EXC_STORE(r10,DEAR)
 	mfspr	r10,SPRN_ESR
 	SPECIAL_EXC_STORE(r10,ESR)
 
-	lbz	r10,PACAIRQSOFTMASK(r13)
-	SPECIAL_EXC_STORE(r10,SOFTE)
 	ld	r10,_NIP(r1)
 	SPECIAL_EXC_STORE(r10,CSRR0)
 	ld	r10,_MSR(r1)
@@ -194,27 +187,6 @@ BEGIN_FTR_SECTION
 	mtspr	SPRN_MAS8,r10
 END_FTR_SECTION_IFSET(CPU_FTR_EMB_HV)
 
-	lbz	r6,PACAIRQSOFTMASK(r13)
-	ld	r5,SOFTE(r1)
-
-	/* Interrupts had better not already be enabled... */
-	tweqi	r6,IRQS_ENABLED
-
-	andi.	r6,r5,IRQS_DISABLED
-	bne	1f
-
-	TRACE_ENABLE_INTS
-	stb	r5,PACAIRQSOFTMASK(r13)
-1:
-	/*
-	 * Restore PACAIRQHAPPENED rather than setting it based on
-	 * the return MSR[EE], since we could have interrupted
-	 * interrupt replay or other inconsistent transitory
-	 * states that must remain that way.
-	 */
-	SPECIAL_EXC_LOAD(r10,IRQHAPPENED)
-	stb	r10,PACAIRQHAPPENED(r13)
-
 	SPECIAL_EXC_LOAD(r10,DEAR)
 	mtspr	SPRN_DEAR,r10
 	SPECIAL_EXC_LOAD(r10,ESR)
@@ -566,7 +538,7 @@ __end_interrupts:
 	bl	special_reg_save
 	CHECK_NAPPING();
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	bl	unknown_exception
+	bl	unknown_nmi_exception
 	b	ret_from_crit_except
 
 /* Machine Check Interrupt */
@@ -702,7 +674,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
 #ifdef CONFIG_BOOKE_WDT
 	bl	WatchdogException
 #else
-	bl	unknown_exception
+	bl	unknown_nmi_exception
 #endif
 	b	ret_from_crit_except
 
@@ -886,7 +858,7 @@ kernel_dbg_exc:
 	bl	special_reg_save
 	CHECK_NAPPING();
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	bl	unknown_exception
+	bl	unknown_nmi_exception
 	b	ret_from_crit_except
 
 /*
@@ -910,7 +882,7 @@ kernel_dbg_exc:
 	bl	special_reg_save
 	CHECK_NAPPING();
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	bl	unknown_exception
+	bl	unknown_nmi_exception
 	b	ret_from_crit_except
 
 /* Hypervisor call */

arch/powerpc/kernel/traps.c

@@ -1078,6 +1078,16 @@ DEFINE_INTERRUPT_HANDLER_ASYNC(unknown_async_exception)
 	_exception(SIGTRAP, regs, TRAP_UNK, 0);
 }
 
+DEFINE_INTERRUPT_HANDLER_NMI(unknown_nmi_exception)
+{
+	printk("Bad trap at PC: %lx, SR: %lx, vector=%lx\n",
+	       regs->nip, regs->msr, regs->trap);
+
+	_exception(SIGTRAP, regs, TRAP_UNK, 0);
+
+	return 0;
+}
+
 DEFINE_INTERRUPT_HANDLER(instruction_breakpoint_exception)
 {
 	if (notify_die(DIE_IABR_MATCH, "iabr_match", regs, 5,
@@ -2181,10 +2191,11 @@ void __attribute__ ((weak)) WatchdogHandler(struct pt_regs *regs)
 	return;
 }
 
-DEFINE_INTERRUPT_HANDLER(WatchdogException) /* XXX NMI? async? */
+DEFINE_INTERRUPT_HANDLER_NMI(WatchdogException)
 {
 	printk (KERN_EMERG "PowerPC Book-E Watchdog Exception\n");
 	WatchdogHandler(regs);
+	return 0;
 }
 #endif