About KDB global and local hardware breakpoint support in IA32.

[Keith Owens]

On Thu, 13 Feb 2003 15:59:45 +0800, 
"Zhang, Sonic" <sonic.zhang at intel.com> wrote:
>	Current implementation in kdb-v3.0-2.4.20 sees a local breakpoint as
>an equivalence of a global breakpoint. All CPUs share the same data
>structure for hardware debug registers. And each CPU sets its debug register
>for a hardware breakpoint, no matter whether it is a local one of the other
>CPUs.

Where do you get that from?  kdb_bp_install_local() is

void
kdb_bp_install_local(struct pt_regs *regs)
{
	int i;

	for(i=0; i<KDB_MAXBPT; i++) {
		if (KDB_DEBUG(BP)) {
			kdb_printf("kdb_bp_install_local bp %d bp_enabled %d bp_global %d cpu %d bp_cpu %d\n",
				i, kdb_breakpoints[i].bp_enabled, kdb_breakpoints[i].bp_global,
				smp_processor_id(), kdb_breakpoints[i].bp_cpu);
		}
		if (kdb_breakpoints[i].bp_enabled
		 && kdb_breakpoints[i].bp_cpu == smp_processor_id()
		 && !kdb_breakpoints[i].bp_global){
			kdba_installbp(regs, &kdb_breakpoints[i]);
		}
	}
}

That function is called for each cpu as it leaves kdb.  It only
installs local breakpoints for the current cpu.

kdb_bp() has
	if (hardware && !global) {
		bp->bp_global = 0;
		bp->bp_cpu = smp_processor_id();
	}
marking local breakpoints by their cpu number.