x86: debugctlmsr context switch
This adds low-level support for a per-thread value of MSR_IA32_DEBUGCTLMSR.
The per-thread value is switched in when TIF_DEBUGCTLMSR is set.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index d9905c9..d5462f2 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -602,10 +602,14 @@
__switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
struct tss_struct *tss)
{
- struct thread_struct *next;
+ struct thread_struct *prev, *next;
+ prev = &prev_p->thread;
next = &next_p->thread;
+ if (next->debugctlmsr != prev->debugctlmsr)
+ wrmsr(MSR_IA32_DEBUGCTLMSR, next->debugctlmsr, 0);
+
if (test_tsk_thread_flag(next_p, TIF_DEBUG)) {
set_debugreg(next->debugreg[0], 0);
set_debugreg(next->debugreg[1], 1);
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index f7356e5..ae5eca1 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -555,6 +555,9 @@
prev = &prev_p->thread,
next = &next_p->thread;
+ if (next->debugctlmsr != prev->debugctlmsr)
+ wrmsrl(MSR_IA32_DEBUGCTLMSR, next->debugctlmsr);
+
if (test_tsk_thread_flag(next_p, TIF_DEBUG)) {
loaddebug(next, 0);
loaddebug(next, 1);