[PATCH] x86-64: x86_64 make NMI use PERFCTR1 for architectural perfmon (take 2)

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 <eranian@hpl.hp.com>

Signed-off-by: Andi Kleen <ak@suse.de>

diff --git a/arch/x86_64/kernel/nmi.c b/arch/x86_64/kernel/nmi.c
index dfab9f1..010d3d9 100644 (file)
--- a/arch/x86_64/kernel/nmi.c
+++ b/arch/x86_64/kernel/nmi.c
@@ -348,7 +348,7 @@ 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);
        }
 
@@ -713,8 +713,8 @@ static int setup_intel_arch_watchdog(void)
            (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(-1, perfctr_msr))
                goto fail;
@@ -958,7 +958,7 @@ int __kprobes nmi_watchdog_tick(struct pt_regs * regs, unsigned reason)
                                /* 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