From 252988cbf037f3d446eea222afb46cc134d32c71 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Sun, 1 Apr 2018 15:50:36 +1000 Subject: powerpc: Don't write to DABR on >= Power8 if DAWR is disabled flush_thread() calls __set_breakpoint() via set_debug_reg_defaults() without checking ppc_breakpoint_available(). On Power8 or later CPUs which have the DAWR feature disabled that will cause a write to the DABR which is incorrect as those CPUs don't have a DABR. Fix it two ways, by checking ppc_breakpoint_available() in set_debug_reg_defaults(), and also by reworking __set_breakpoint() to only write to DABR on Power7 or earlier. Fixes: 9654153158d3 ("powerpc: Disable DAWR in the base POWER9 CPU features") Signed-off-by: Nicholas Piggin [mpe: Rework the logic in __set_breakpoint()] Signed-off-by: Michael Ellerman --- arch/powerpc/kernel/process.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'arch/powerpc') diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 24a591b4dbe9..1237f13fed51 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 */ @@ -815,9 +816,14 @@ void __set_breakpoint(struct arch_hw_breakpoint *brk) memcpy(this_cpu_ptr(¤t_brk), brk, sizeof(*brk)); if (cpu_has_feature(CPU_FTR_DAWR)) + // Power8 or later set_dawr(brk); - else + else if (!cpu_has_feature(CPU_FTR_ARCH_207S)) + // Power7 or earlier set_dabr(brk); + else + // Shouldn't happen due to higher level checks + WARN_ON_ONCE(1); } void set_breakpoint(struct arch_hw_breakpoint *brk) -- cgit v1.2.3