Messages in this thread Patch in this message |  | | Date | Sat, 17 Feb 2007 08:06:56 -0800 | From | Stephane Eranian <> | Subject | [PATCH] i386 make NMI use PERFCTR1 for architectural perfmon |
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Hello,
This patch against 2.6.20 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 <eranian@hpl.hp.com>
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 2007-02-04 10:44:54.000000000 -0800 +++ linux-2.6.20.base/arch/i386/kernel/nmi.c 2007-02-17 07:59:41.000000000 -0800 @@ -288,7 +288,7 @@ static int __init check_nmi_watchdog(voi * 32nd bit should be 1, for 33.. to be 1. * Find the appropriate nmi_hz */ - if (wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR0 && + if (wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR1 && ((u64)cpu_khz * 1000) > 0x7fffffffULL) { u64 count = (u64)cpu_khz * 1000; do_div(count, 0x7fffffffUL); @@ -685,8 +685,8 @@ 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; @@ -958,7 +958,7 @@ __kprobes int nmi_watchdog_tick(struct p apic_write(APIC_LVTPC, APIC_DM_NMI); } 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. -- -Stephane - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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