Subject: [PATCH 2/2] powerpc: Fix DABR write in the case of DAWR disabled

From: Nicholas Piggin <[email-masked]>
Date: Sun, 1 Apr 2018 15:50:36 +1000

flush_thread will call set_breakpoint via set_debug_reg_defaults,
and cause POWER8 and above CPUs without the DAWR feature to try
to write to DAWR.

Cc: Michael Neuling <[email-masked]>
Signed-off-by: Nicholas Piggin <[email-masked]>
---
 arch/powerpc/kernel/process.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 24a591b4dbe9..bfcf5437083c 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -718,7 +718,8 @@ static void set_debug_reg_defaults(struct thread_struct *thread)
 {
 	thread->hw_brk.address = 0;
 	thread->hw_brk.type = 0;
-	set_breakpoint(&thread->hw_brk);
+	if (ppc_breakpoint_available())
+		set_breakpoint(&thread->hw_brk);
 }
 #endif /* !CONFIG_HAVE_HW_BREAKPOINT */
 #endif	/* CONFIG_PPC_ADV_DEBUG_REGS */
@@ -814,10 +815,14 @@ void __set_breakpoint(struct arch_hw_breakpoint *brk)
 {
 	memcpy(this_cpu_ptr(&current_brk), brk, sizeof(*brk));
 
-	if (cpu_has_feature(CPU_FTR_DAWR))
-		set_dawr(brk);
-	else
+	if (cpu_has_feature(CPU_FTR_ARCH_207S)) {
+		if (cpu_has_feature(CPU_FTR_DAWR))
+			set_dawr(brk);
+		else
+			WARN_ON_ONCE(1);
+	} else {
 		set_dabr(brk);
+	}
 }
 
 void set_breakpoint(struct arch_hw_breakpoint *brk)
-- 
2.16.3