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Subject[PATCH x86 for review II] [11/39] i386: Handle 32 bit PerfMon Counter writes cleanly in i386 nmi_watchdog
Date

From: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>

Change i386 nmi handler to handle 32 bit perfmon counter MSR writes cleanly.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>

---
arch/i386/kernel/nmi.c | 64 ++++++++++++++++++++++++++++++++++++-------------
1 file changed, 48 insertions(+), 16 deletions(-)
Index: linux/arch/i386/kernel/nmi.c
===================================================================
--- linux.orig/arch/i386/kernel/nmi.c
+++ linux/arch/i386/kernel/nmi.c
@@ -216,6 +216,28 @@ static __init void nmi_cpu_busy(void *da
}
#endif

+static unsigned int adjust_for_32bit_ctr(unsigned int hz)
+{
+ u64 counter_val;
+ unsigned int retval = hz;
+
+ /*
+ * On Intel CPUs with P6/ARCH_PERFMON only 32 bits in the counter
+ * are writable, with higher bits sign extending from bit 31.
+ * So, we can only program the counter with 31 bit values and
+ * 32nd bit should be 1, for 33.. to be 1.
+ * Find the appropriate nmi_hz
+ */
+ counter_val = (u64)cpu_khz * 1000;
+ do_div(counter_val, retval);
+ if (counter_val > 0x7fffffffULL) {
+ u64 count = (u64)cpu_khz * 1000;
+ do_div(count, 0x7fffffffUL);
+ retval = count + 1;
+ }
+ return retval;
+}
+
static int __init check_nmi_watchdog(void)
{
unsigned int *prev_nmi_count;
@@ -281,18 +303,10 @@ static int __init check_nmi_watchdog(voi
struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);

nmi_hz = 1;
- /*
- * On Intel CPUs with ARCH_PERFMON only 32 bits in the counter
- * are writable, with higher bits sign extending from bit 31.
- * So, we can only program the counter with 31 bit values and
- * 32nd bit should be 1, for 33.. to be 1.
- * Find the appropriate nmi_hz
- */
- if (wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR0 &&
- ((u64)cpu_khz * 1000) > 0x7fffffffULL) {
- u64 count = (u64)cpu_khz * 1000;
- do_div(count, 0x7fffffffUL);
- nmi_hz = count + 1;
+
+ if (wd->perfctr_msr == MSR_P6_PERFCTR0 ||
+ wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR0) {
+ nmi_hz = adjust_for_32bit_ctr(nmi_hz);
}
}

@@ -442,6 +456,17 @@ static void write_watchdog_counter(unsig
wrmsrl(perfctr_msr, 0 - count);
}

+static void write_watchdog_counter32(unsigned int perfctr_msr,
+ const char *descr)
+{
+ u64 count = (u64)cpu_khz * 1000;
+
+ do_div(count, nmi_hz);
+ if(descr)
+ Dprintk("setting %s to -0x%08Lx\n", descr, count);
+ wrmsr(perfctr_msr, (u32)(-count), 0);
+}
+
/* Note that these events don't tick when the CPU idles. This means
the frequency varies with CPU load. */

@@ -531,7 +556,8 @@ static int setup_p6_watchdog(void)

/* setup the timer */
wrmsr(evntsel_msr, evntsel, 0);
- write_watchdog_counter(perfctr_msr, "P6_PERFCTR0");
+ nmi_hz = adjust_for_32bit_ctr(nmi_hz);
+ write_watchdog_counter32(perfctr_msr, "P6_PERFCTR0");
apic_write(APIC_LVTPC, APIC_DM_NMI);
evntsel |= P6_EVNTSEL0_ENABLE;
wrmsr(evntsel_msr, evntsel, 0);
@@ -704,7 +730,8 @@ static int setup_intel_arch_watchdog(voi

/* setup the timer */
wrmsr(evntsel_msr, evntsel, 0);
- write_watchdog_counter(perfctr_msr, "INTEL_ARCH_PERFCTR0");
+ nmi_hz = adjust_for_32bit_ctr(nmi_hz);
+ write_watchdog_counter32(perfctr_msr, "INTEL_ARCH_PERFCTR0");
apic_write(APIC_LVTPC, APIC_DM_NMI);
evntsel |= ARCH_PERFMON_EVENTSEL0_ENABLE;
wrmsr(evntsel_msr, evntsel, 0);
@@ -956,6 +983,8 @@ __kprobes int nmi_watchdog_tick(struct p
dummy &= ~P4_CCCR_OVF;
wrmsrl(wd->cccr_msr, dummy);
apic_write(APIC_LVTPC, APIC_DM_NMI);
+ /* start the cycle over again */
+ write_watchdog_counter(wd->perfctr_msr, NULL);
}
else if (wd->perfctr_msr == MSR_P6_PERFCTR0 ||
wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR0) {
@@ -964,9 +993,12 @@ __kprobes int nmi_watchdog_tick(struct p
* other P6 variant.
* ArchPerfom/Core Duo also needs this */
apic_write(APIC_LVTPC, APIC_DM_NMI);
+ /* P6/ARCH_PERFMON has 32 bit counter write */
+ write_watchdog_counter32(wd->perfctr_msr, NULL);
+ } else {
+ /* start the cycle over again */
+ write_watchdog_counter(wd->perfctr_msr, NULL);
}
- /* start the cycle over again */
- write_watchdog_counter(wd->perfctr_msr, NULL);
rc = 1;
} else if (nmi_watchdog == NMI_IO_APIC) {
/* don't know how to accurately check for this.
-
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