[PATCH AUTOSEL for 4.15 088/102] powerpc/64: Don't trace irqs-off at interrupt return to soft-disabled context

[Sasha Levin]

From: Nicholas Piggin <npiggin@xxxxxxxxx>

[ Upstream commit acb1feab320e38588fccc568e3767761f494976f ]

When an interrupt is returning to a soft-disabled context (which can
happen for non-maskable interrupts or synchronous interrupts), it goes
through the motions of soft-disabling again, including calling
TRACE_DISABLE_INTS (i.e., trace_hardirqs_off()).

This is not necessary, because we must already be soft-disabled in the
interrupt context, it also may be causing crashes in the irq tracing
code to re-enter as an nmi. Replace it with a warning to ensure that
soft-interrupts are still disabled.

Fixes: 7c0482e3d055 ("powerpc/irq: Fix another case of lazy IRQ state getting out of sync")
Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
---
 arch/powerpc/kernel/entry_64.S | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 2748584b767d..fde89f04f276 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -939,9 +939,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	beq	1f
 	rlwinm	r7,r7,0,~PACA_IRQ_HARD_DIS
 	stb	r7,PACAIRQHAPPENED(r13)
-1:	li	r0,0
-	stb	r0,PACASOFTIRQEN(r13);
-	TRACE_DISABLE_INTS
+1:
+#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_BUG)
+	/* The interrupt should not have soft enabled. */
+	lbz	r7,PACASOFTIRQEN(r13)
+1:	tdnei	r7,0
+	EMIT_BUG_ENTRY 1b,__FILE__,__LINE__,BUGFLAG_WARNING
+#endif
 	b	.Ldo_restore
 
 	/*
-- 
2.14.1