Hello, This patch against 2.6.20-git14 makes the NMI watchdog use PERFSEL1/PERFCTR1 instead of PERFSEL0/PERFCTR0 on processors supporting Intel architectural perfmon, such as Intel Core 2. Although all PMU events can work on both counters, the Precise Event-Based Sampling (PEBS) requires that the event be in PERFCTR0 to work correctly (see section 18.14.4.1 in the IA32 SDM Vol 3b).
A similar patch for x86-64 is to follow. Changelog: - make the i386 NMI watchdog use PERFSEL1/PERFCTR1 instead of PERFSEL0/PERFCTR0 on processors supporting the Intel architectural perfmon (e.g. Core 2 Duo). This allows PEBS to work when the NMI watchdog is active. signed-off-by: stephane eranian <[EMAIL PROTECTED]> diff -urNp --exclude=.git linux-2.6.20.orig/arch/i386/kernel/nmi.c linux-2.6.20.base/arch/i386/kernel/nmi.c --- linux-2.6.20.orig/arch/i386/kernel/nmi.c 2007-02-19 13:37:26.000000000 -0800 +++ linux-2.6.20.base/arch/i386/kernel/nmi.c 2007-02-19 13:54:42.000000000 -0800 @@ -307,7 +307,7 @@ static int __init check_nmi_watchdog(voi nmi_hz = 1; if (wd->perfctr_msr == MSR_P6_PERFCTR0 || - wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR0) { + wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR1) { nmi_hz = adjust_for_32bit_ctr(nmi_hz); } } @@ -741,8 +741,8 @@ static int setup_intel_arch_watchdog(voi (ebx & ARCH_PERFMON_UNHALTED_CORE_CYCLES_PRESENT)) goto fail; - perfctr_msr = MSR_ARCH_PERFMON_PERFCTR0; - evntsel_msr = MSR_ARCH_PERFMON_EVENTSEL0; + perfctr_msr = MSR_ARCH_PERFMON_PERFCTR1; + evntsel_msr = MSR_ARCH_PERFMON_EVENTSEL1; if (!reserve_perfctr_nmi(perfctr_msr)) goto fail; @@ -1022,7 +1022,7 @@ __kprobes int nmi_watchdog_tick(struct p write_watchdog_counter(wd->perfctr_msr, NULL); } else if (wd->perfctr_msr == MSR_P6_PERFCTR0 || - wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR0) { + wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR1) { /* P6 based Pentium M need to re-unmask * the apic vector but it doesn't hurt * other P6 variant. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/