Re: nmi_watchdog=2 regression in 2.6.21

[Stephane Eranian <eranian@hpl.hp.com>]

Daniel,

On Fri, Aug 31, 2007 at 07:43:20AM -0700, Daniel Walker wrote:
> On Thu, 2007-08-30 at 14:05 -0700, Stephane Eranian wrote:
> > Daniel,
> 
> > Yes, I realized I missed a small detail in the switch statement.
> > Could you try the new version?
> 
> This patch still has the stuck NMI .. Essentially the same thing that
> happened without the patch..
> 
Ok, looks like deaulting to P6 does not quite work.

Here is a new version. This time I used a different approach.
I am must admit I am a bit puzzled by the duplication of information
between the wd_ops and the nmi_watchdog_ctlblk structure. My understanding
is that thelater is used as a cache for the info that needs to be per-cpu.

The wd_ops provides the MSR to use for the counter, yet all the setup_*()
routines hardcode the MSR. Not sure why?

In this patch, the setup_*() routine now extract the MSR from the wd_ops
to copy them into the nmi_watchdog_ctlblk. This is not done for P4 because
of the special and ugly case of HT. 

With this approach, we can now create a custom wd_ops for CoreDuo that is
a clone of the intel_arch_wd_ops, except for the MSR.

Could you try this one instead?

Thanks.

-- 

-Stephane

diff --git a/arch/i386/kernel/cpu/perfctr-watchdog.c b/arch/i386/kernel/cpu/perfctr-watchdog.c
index 9b5d6af..f9066e1 100644
--- a/arch/i386/kernel/cpu/perfctr-watchdog.c
+++ b/arch/i386/kernel/cpu/perfctr-watchdog.c
@@ -271,8 +271,8 @@ static int setup_k7_watchdog(unsigned nmi_hz)
 	unsigned int evntsel;
 	struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);
 
-	perfctr_msr = MSR_K7_PERFCTR0;
-	evntsel_msr = MSR_K7_EVNTSEL0;
+	perfctr_msr = wd_ops->perfctr;
+	evntsel_msr = wd_ops->evntsel;
 
 	wrmsrl(perfctr_msr, 0UL);
 
@@ -351,8 +351,8 @@ static int setup_p6_watchdog(unsigned nmi_hz)
 	unsigned int evntsel;
 	struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);
 
-	perfctr_msr = MSR_P6_PERFCTR0;
-	evntsel_msr = MSR_P6_EVNTSEL0;
+	perfctr_msr = wd_ops->perfctr;
+	evntsel_msr = wd_ops->evntsel;
 
 	/* KVM doesn't implement this MSR */
 	if (wrmsr_safe(perfctr_msr, 0, 0) < 0)
@@ -577,8 +577,8 @@ static int setup_intel_arch_watchdog(unsigned nmi_hz)
 	    (ebx & ARCH_PERFMON_UNHALTED_CORE_CYCLES_PRESENT))
 		return 0;
 
-	perfctr_msr = MSR_ARCH_PERFMON_PERFCTR1;
-	evntsel_msr = MSR_ARCH_PERFMON_EVENTSEL1;
+	perfctr_msr = wd_ops->perfctr;
+	evntsel_msr = wd_ops->evntsel;
 
 	wrmsrl(perfctr_msr, 0UL);
 
@@ -613,6 +613,16 @@ static struct wd_ops intel_arch_wd_ops = {
 	.evntsel = MSR_ARCH_PERFMON_EVENTSEL1,
 };
 
+static struct wd_ops coreduo_wd_ops = {
+	.reserve = single_msr_reserve,
+	.unreserve = single_msr_unreserve,
+	.setup = setup_intel_arch_watchdog,
+	.rearm = p6_rearm,
+	.stop = single_msr_stop_watchdog,
+	.perfctr = MSR_ARCH_PERFMON_PERFCTR0,
+	.evntsel = MSR_ARCH_PERFMON_EVENTSEL0,
+};
+
 static void probe_nmi_watchdog(void)
 {
 	switch (boot_cpu_data.x86_vendor) {
@@ -623,6 +633,10 @@ static void probe_nmi_watchdog(void)
 		wd_ops = &k7_wd_ops;
 		break;
 	case X86_VENDOR_INTEL:
+		if (boot_cpu_data.x86 == 6 && boot_cpu_data.x86_model == 14) {
+			wd_ops = &coreduo_wd_ops;
+			break;
+		}
 		if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON)) {
 			wd_ops = &intel_arch_wd_ops;
 			break;