diff --git a/arch/x86/include/asm/ds.h b/arch/x86/include/asm/ds.h
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 5ca01e3..c4eddd8 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -430,7 +430,7 @@ struct thread_struct {
 	/* Max allowed port in the bitmap, in bytes: */
 	unsigned		io_bitmap_max;
 /* MSR_IA32_DEBUGCTLMSR value to switch in if TIF_DEBUGCTLMSR is set.  */
-	unsigned long	debugctlmsr;
+	unsigned long	debugctlval;
 #ifdef CONFIG_X86_DS
 /* Debug Store context; see include/asm-x86/ds.h; goes into MSR_IA32_DS_AREA */
 	struct ds_context	*ds_ctx;
@@ -752,13 +752,21 @@ extern void switch_to_new_gdt(void);
 extern void cpu_init(void);
 extern void init_gdt(int cpu);
 
-static inline void update_debugctlmsr(unsigned long debugctlmsr)
+static inline void update_debugctlmsr(unsigned long val, unsigned long mask)
 {
+	unsigned long ctl;
+	unsigned long flags;
 #ifndef CONFIG_X86_DEBUGCTLMSR
 	if (boot_cpu_data.x86 < 6)
 		return;
 #endif
-	wrmsrl(MSR_IA32_DEBUGCTLMSR, debugctlmsr);
+	local_irq_save(flags);
+
+	rdmsrl(MSR_IA32_DEBUGCTLMSR, ctl);
+	ctl = (ctl & ~mask) | (val & mask);
+	wrmsrl(MSR_IA32_DEBUGCTLMSR, ctl);
+
+	local_irq_restore(flags);
 }
 
 /*
diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index 6c27679..fcb034a 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -410,13 +410,13 @@ static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 static void __kprobes clear_btf(void)
 {
 	if (test_thread_flag(TIF_DEBUGCTLMSR))
-		update_debugctlmsr(0);
+		update_debugctlmsr(0, DEBUGCTLMSR_BTF);
 }
 
 static void __kprobes restore_btf(void)
 {
 	if (test_thread_flag(TIF_DEBUGCTLMSR))
-		update_debugctlmsr(current->thread.debugctlmsr);
+		update_debugctlmsr(DEBUGCTLMSR_BTF, DEBUGCTLMSR_BTF);
 }
 
 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index ce578b2..73ad19a 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -254,8 +254,6 @@ void exit_thread(void)
 #ifdef CONFIG_X86_DS
 	/* Free any DS contexts that have not been properly released. */
 	if (unlikely(current->thread.ds_ctx)) {
-		/* we clear debugctl to make sure DS is not used. */
-		update_debugctlmsr(0);
 		ds_free(current->thread.ds_ctx);
 	}
 #endif /* CONFIG_X86_DS */
@@ -424,8 +422,8 @@ int set_tsc_mode(unsigned int val)
 }
 
 #ifdef CONFIG_X86_DS
-static int update_debugctl(struct thread_struct *prev,
-			struct thread_struct *next, unsigned long debugctl)
+static void switch_ds_area(struct thread_struct *prev,
+			struct thread_struct *next)
 {
 	unsigned long ds_prev = 0;
 	unsigned long ds_next = 0;
@@ -435,20 +433,13 @@ static int update_debugctl(struct thread_struct *prev,
 	if (next->ds_ctx)
 		ds_next = (unsigned long)next->ds_ctx->ds;
 
-	if (ds_next != ds_prev) {
-		/* we clear debugctl to make sure DS
-		 * is not in use when we change it */
-		debugctl = 0;
-		update_debugctlmsr(0);
+	if (ds_next != ds_prev)
 		wrmsr(MSR_IA32_DS_AREA, ds_next, 0);
-	}
-	return debugctl;
 }
 #else
-static int update_debugctl(struct thread_struct *prev,
-			struct thread_struct *next, unsigned long debugctl)
+static void swich_ds_area(struct thread_struct *prev,
+			struct thread_struct *next)
 {
-	return debugctl;
 }
 #endif /* CONFIG_X86_DS */
 
@@ -457,7 +448,6 @@ __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
 		 struct tss_struct *tss)
 {
 	struct thread_struct *prev, *next;
-	unsigned long debugctl;
 
 	prev = &prev_p->thread;
 	next = &next_p->thread;
@@ -465,10 +455,13 @@ __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
 	if (test_tsk_thread_flag(prev_p, TIF_PERFMON_CTXSW))
 		pfm_ctxsw_out(prev_p, next_p);
 
-	debugctl = update_debugctl(prev, next, prev->debugctlmsr);
+	if (test_tsk_thread_flag(prev_p, TIF_DEBUGCTLMSR))
+		update_debugctlmsr(0, prev->debugctlval);
+
+	switch_ds_area(prev, next);
 
-	if (next->debugctlmsr != debugctl)
-		update_debugctlmsr(next->debugctlmsr);
+	if (test_tsk_thread_flag(next_p, TIF_DEBUGCTLMSR))
+		update_debugctlmsr(next->debugctlval, next->debugctlval);
 
 	if (test_tsk_thread_flag(next_p, TIF_PERFMON_CTXSW))
 		pfm_ctxsw_in(prev_p, next_p);
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 9c6ff7a..250a9fd 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -236,13 +236,17 @@ void exit_thread(void)
 		t->io_bitmap_max = 0;
 		put_cpu();
 	}
+
+	/* clear debugctl if used */
+	if (test_tsk_thread_flag(me, TIF_DEBUGCTLMSR)) {
+		update_debugctlmsr(0, t->debugctlval);
+		clear_tsk_thread_flag(me, TIF_DEBUGCTLMSR);
+	}
+
 #ifdef CONFIG_X86_DS
 	/* Free any DS contexts that have not been properly released. */
-	if (unlikely(t->ds_ctx)) {
-		/* we clear debugctl to make sure DS is not used. */
-		update_debugctlmsr(0);
+	if (unlikely(t->ds_ctx))
 		ds_free(t->ds_ctx);
-	}
 #endif /* CONFIG_X86_DS */
 
 	pfm_exit_thread();
@@ -475,7 +479,6 @@ static inline void __switch_to_xtra(struct task_struct *prev_p,
 				    struct tss_struct *tss)
 {
 	struct thread_struct *prev, *next;
-	unsigned long debugctl;
 
 	prev = &prev_p->thread,
 	next = &next_p->thread;
@@ -483,7 +486,8 @@ static inline void __switch_to_xtra(struct task_struct *prev_p,
 	if (test_tsk_thread_flag(prev_p, TIF_PERFMON_CTXSW))
 		pfm_ctxsw_out(prev_p, next_p);
 
-	debugctl = prev->debugctlmsr;
+	if (test_tsk_thread_flag(prev_p, TIF_DEBUGCTLMSR))
+		update_debugctlmsr(0, prev->debugctlval);
 
 #ifdef CONFIG_X86_DS
 	{
@@ -494,20 +498,13 @@ static inline void __switch_to_xtra(struct task_struct *prev_p,
 		if (next->ds_ctx)
 			ds_next = (unsigned long)next->ds_ctx->ds;
 
-		if (ds_next != ds_prev) {
-			/*
-			 * We clear debugctl to make sure DS
-			 * is not in use when we change it:
-			 */
-			debugctl = 0;
-			update_debugctlmsr(0);
+		if (ds_next != ds_prev)
 			wrmsrl(MSR_IA32_DS_AREA, ds_next);
-		}
 	}
 #endif /* CONFIG_X86_DS */
 
-	if (next->debugctlmsr != debugctl)
-		update_debugctlmsr(next->debugctlmsr);
+	if (test_tsk_thread_flag(next_p, TIF_DEBUGCTLMSR))
+		update_debugctlmsr(next->debugctlval, next->debugctlval);
 
 	if (test_tsk_thread_flag(next_p, TIF_PERFMON_CTXSW))
 		pfm_ctxsw_in(prev_p, next_p);
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 0a6d8c1..6c62c92 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -786,9 +786,9 @@ static int ptrace_bts_config(struct task_struct *child,
 		goto errout;
 
 	if (cfg.flags & PTRACE_BTS_O_TRACE)
-		child->thread.debugctlmsr |= bts_cfg.debugctl_mask;
+		child->thread.debugctlval |= bts_cfg.debugctl_mask;
 	else
-		child->thread.debugctlmsr &= ~bts_cfg.debugctl_mask;
+		child->thread.debugctlval &= ~bts_cfg.debugctl_mask;
 
 	if (cfg.flags & PTRACE_BTS_O_SCHED)
 		set_tsk_thread_flag(child, TIF_BTS_TRACE_TS);
@@ -798,7 +798,7 @@ static int ptrace_bts_config(struct task_struct *child,
 	error = sizeof(cfg);
 
 out:
-	if (child->thread.debugctlmsr)
+	if (child->thread.debugctlval)
 		set_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
 	else
 		clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
@@ -806,7 +806,7 @@ out:
 	return error;
 
 errout:
-	child->thread.debugctlmsr &= ~bts_cfg.debugctl_mask;
+	child->thread.debugctlval &= ~bts_cfg.debugctl_mask;
 	clear_tsk_thread_flag(child, TIF_BTS_TRACE_TS);
 	goto out;
 }
@@ -844,7 +844,7 @@ static int ptrace_bts_status(struct task_struct *child,
 		cfg.flags |= PTRACE_BTS_O_SIGNAL;
 
 	if (test_tsk_thread_flag(child, TIF_DEBUGCTLMSR) &&
-	    child->thread.debugctlmsr & bts_cfg.debugctl_mask)
+	    child->thread.debugctlval & bts_cfg.debugctl_mask)
 		cfg.flags |= PTRACE_BTS_O_TRACE;
 
 	if (test_tsk_thread_flag(child, TIF_BTS_TRACE_TS))
@@ -975,8 +975,8 @@ void ptrace_disable(struct task_struct *child)
 #ifdef CONFIG_X86_PTRACE_BTS
 	(void)ds_release_bts(child);
 
-	child->thread.debugctlmsr &= ~bts_cfg.debugctl_mask;
-	if (!child->thread.debugctlmsr)
+	child->thread.debugctlval &= ~bts_cfg.debugctl_mask;
+	if (!child->thread.debugctlval)
 		clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
 
 	clear_tsk_thread_flag(child, TIF_BTS_TRACE_TS);
diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c
index e8b9863..e4b35ee 100644
--- a/arch/x86/kernel/step.c
+++ b/arch/x86/kernel/step.c
@@ -161,17 +161,30 @@ static int enable_single_step(struct task_struct *child)
 /*
  * Install this value in MSR_IA32_DEBUGCTLMSR whenever child is running.
  */
-static void write_debugctlmsr(struct task_struct *child, unsigned long val)
+static inline void set_btf(struct task_struct *child)
 {
-	if (child->thread.debugctlmsr == val)
+	if (child->thread.debugctlval & DEBUGCTLMSR_BTF)
 		return;
 
-	child->thread.debugctlmsr = val;
+	child->thread.debugctlval |= DEBUGCTLMSR_BTF;
 
 	if (child != current)
 		return;
 
-	update_debugctlmsr(val);
+	update_debugctlmsr(child->thread.debugctlval, DEBUGCTLMSR_BTF);
+}
+
+static inline void clear_btf(struct task_struct *child)
+{
+	if (!(child->thread.debugctlval& DEBUGCTLMSR_BTF))
+		return;
+
+	 child->thread.debugctlval &= ~DEBUGCTLMSR_BTF;
+
+	if (child != current)
+		return;
+
+	update_debugctlmsr(child->thread.debugctlval, DEBUGCTLMSR_BTF);
 }
 
 /*
@@ -188,13 +201,10 @@ static void enable_step(struct task_struct *child, bool block)
 	 */
 	if (enable_single_step(child) && block) {
 		set_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
-		write_debugctlmsr(child,
-				  child->thread.debugctlmsr | DEBUGCTLMSR_BTF);
+		set_btf(child);
 	} else {
-		write_debugctlmsr(child,
-				  child->thread.debugctlmsr & ~DEBUGCTLMSR_BTF);
-
-		if (!child->thread.debugctlmsr)
+		clear_btf(child);
+		if (!child->thread.debugctlval)
 			clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
 	}
 }
@@ -214,10 +224,9 @@ void user_disable_single_step(struct task_struct *child)
 	/*
 	 * Make sure block stepping (BTF) is disabled.
 	 */
-	write_debugctlmsr(child,
-			  child->thread.debugctlmsr & ~DEBUGCTLMSR_BTF);
+	clear_btf(child);
 
-	if (!child->thread.debugctlmsr)
+	if (!child->thread.debugctlval)
 		clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
 
 	/* Always clear TIF_SINGLESTEP... */
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 04d242a..dd9a86a 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -582,7 +582,7 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
 	 * The processor cleared BTF, so don't mark that we need it set.
 	 */
 	clear_tsk_thread_flag(tsk, TIF_DEBUGCTLMSR);
-	tsk->thread.debugctlmsr = 0;
+	tsk->thread.debugctlval &= ~DEBUGCTLMSR_BTF;
 
 	if (notify_die(DIE_DEBUG, "debug", regs, condition, error_code,
 						SIGTRAP) == NOTIFY_STOP)