x86_64 make NMI use PERFCTR1 for architectural perfmon (take 2) From: Stephane Eranian 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). This versions has 3 chunks compared to previous where we had missed on check. Changelog: - make the x86-64 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 Signed-off-by: Andi Kleen --- arch/x86_64/kernel/nmi.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) Index: linux/arch/x86_64/kernel/nmi.c =================================================================== --- linux.orig/arch/x86_64/kernel/nmi.c +++ linux/arch/x86_64/kernel/nmi.c @@ -285,7 +285,7 @@ int __init check_nmi_watchdog (void) struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk); nmi_hz = 1; - if (wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR0) + if (wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR1) nmi_hz = adjust_for_32bit_ctr(nmi_hz); } @@ -650,8 +650,8 @@ 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; @@ -895,7 +895,7 @@ int __kprobes nmi_watchdog_tick(struct p /* start the cycle over again */ wrmsrl(wd->perfctr_msr, -((u64)cpu_khz * 1000 / nmi_hz)); - } else if (wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR0) { + } else if (wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR1) { /* * ArchPerfom/Core Duo needs to re-unmask * the apic vector