linux-kernel - [PATCH v2 4/4] x86: Stop Intel PT and save its registers when panic occurs

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Date:	Tue, 8 Sep 2015 14:49:24 +0900
From:	Takao Indoh <indou.takao@...fujitsu.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>
CC:	<linux-kernel@...r.kernel.org>, <x86@...nel.org>
Subject: [PATCH v2 4/4] x86: Stop Intel PT and save its registers when panic occurs

When panic occurs, Intel PT logging is stopped to prevent it from
overwrite its log buffer. The registers of Intel PT are saved in the
memory on panic, they are needed for debugger to find the last position
where Intel PT wrote data.

Signed-off-by: Takao Indoh <indou.takao@...fujitsu.com>
---
 arch/x86/kernel/crash.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index e068d66..78deceb 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -35,6 +35,7 @@
 #include <asm/cpu.h>
 #include <asm/reboot.h>
 #include <asm/virtext.h>
+#include <asm/intel_pt_log.h>
 
 /* Alignment required for elf header segment */
 #define ELF_CORE_HEADER_ALIGN   4096
@@ -127,6 +128,10 @@ static void kdump_nmi_callback(int cpu, struct pt_regs *regs)
 	cpu_emergency_vmxoff();
 	cpu_emergency_svm_disable();
 
+#ifdef CONFIG_X86_INTEL_PT_LOG
+	save_intel_pt_registers();
+#endif
+
 	disable_local_APIC();
 }
 
@@ -172,6 +177,10 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
 	cpu_emergency_vmxoff();
 	cpu_emergency_svm_disable();
 
+#ifdef CONFIG_X86_INTEL_PT_LOG
+	save_intel_pt_registers();
+#endif
+
 #ifdef CONFIG_X86_IO_APIC
 	/* Prevent crash_kexec() from deadlocking on ioapic_lock. */
 	ioapic_zap_locks();
-- 
1.7.1


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