From: Ingo Molnar <mingo@elte.hu>
Date: Tue, 15 Sep 2009 10:18:15 +0000 (+0200)
Subject: Merge branch 'linus' into tracing/hw-breakpoints
X-Git-Url: http://git.alex.org.uk

Merge branch 'linus' into tracing/hw-breakpoints

Conflicts:
	arch/x86/kernel/process_64.c

Semantic conflict fixed in:
	arch/x86/kvm/x86.c

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

dca2d6ac09d9ef59ff46820d4f0c94b08a671202
diff --cc arch/x86/kernel/process_64.c
index 89c46f1,ad535b6..72edac0
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@@ -493,33 -489,12 +502,30 @@@ __switch_to(struct task_struct *prev_p
  		     task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV))
  		__switch_to_xtra(prev_p, next_p, tss);
  
- 	/* If the task has used fpu the last 5 timeslices, just do a full
- 	 * restore of the math state immediately to avoid the trap; the
- 	 * chances of needing FPU soon are obviously high now
- 	 *
- 	 * tsk_used_math() checks prevent calling math_state_restore(),
- 	 * which can sleep in the case of !tsk_used_math()
+ 	/*
+ 	 * Preload the FPU context, now that we've determined that the
+ 	 * task is likely to be using it. 
  	 */
- 	if (tsk_used_math(next_p) && next_p->fpu_counter > 5)
- 		math_state_restore();
+ 	if (preload_fpu)
+ 		__math_state_restore();
 +	/*
 +	 * There's a problem with moving the arch_install_thread_hw_breakpoint()
 +	 * call before current is updated.  Suppose a kernel breakpoint is
 +	 * triggered in between the two, the hw-breakpoint handler will see that
 +	 * the 'current' task does not have TIF_DEBUG flag set and will think it
 +	 * is leftover from an old task (lazy switching) and will erase it. Then
 +	 * until the next context switch, no user-breakpoints will be installed.
 +	 *
 +	 * The real problem is that it's impossible to update both current and
 +	 * physical debug registers at the same instant, so there will always be
 +	 * a window in which they disagree and a breakpoint might get triggered.
 +	 * Since we use lazy switching, we are forced to assume that a
 +	 * disagreement means that current is correct and the exception is due
 +	 * to lazy debug register switching.
 +	 */
 +	if (unlikely(test_tsk_thread_flag(next_p, TIF_DEBUG)))
 +		arch_install_thread_hw_breakpoint(next_p);
 +
  	return prev_p;
  }
  
diff --cc arch/x86/kvm/x86.c
index 3d45290,be451ee..74029f5
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@@ -3312,18 -3638,17 +3638,17 @@@ static int vcpu_enter_guest(struct kvm_
  		set_debugreg(vcpu->arch.eff_db[3], 3);
  	}
  
- 	KVMTRACE_0D(VMENTRY, vcpu, entryexit);
+ 	trace_kvm_entry(vcpu->vcpu_id);
  	kvm_x86_ops->run(vcpu, kvm_run);
  
- 	if (unlikely(vcpu->arch.switch_db_regs)) {
- 		set_debugreg(0, 7);
- 		set_debugreg(vcpu->arch.host_db[0], 0);
- 		set_debugreg(vcpu->arch.host_db[1], 1);
- 		set_debugreg(vcpu->arch.host_db[2], 2);
- 		set_debugreg(vcpu->arch.host_db[3], 3);
+ 	if (unlikely(vcpu->arch.switch_db_regs || test_thread_flag(TIF_DEBUG))) {
 -		set_debugreg(current->thread.debugreg0, 0);
 -		set_debugreg(current->thread.debugreg1, 1);
 -		set_debugreg(current->thread.debugreg2, 2);
 -		set_debugreg(current->thread.debugreg3, 3);
++		set_debugreg(current->thread.debugreg[0], 0);
++		set_debugreg(current->thread.debugreg[1], 1);
++		set_debugreg(current->thread.debugreg[2], 2);
++		set_debugreg(current->thread.debugreg[3], 3);
+ 		set_debugreg(current->thread.debugreg6, 6);
+ 		set_debugreg(current->thread.debugreg7, 7);
  	}
- 	set_debugreg(vcpu->arch.host_dr6, 6);
- 	set_debugreg(vcpu->arch.host_dr7, 7);
  
  	set_bit(KVM_REQ_KICK, &vcpu->requests);
  	local_irq_enable();