Re: [PATCH v3 08/11] perf/x86: Enable NMI source reporting for perfmon
From: Jacob Pan
Date: Sat Jul 06 2024 - 18:44:45 EST
On Thu, 4 Jul 2024 10:44:23 -0400, "Liang, Kan" <kan.liang@xxxxxxxxxxxxxxx>
wrote:
> On 2024-06-28 4:18 p.m., Jacob Pan wrote:
> > Program the designated NMI source vector into the performance monitoring
> > interrupt (PMI) of the local vector table. PMI handler will be directly
> > invoked when its NMI is generated. This avoids the latency of calling
> > all NMI handlers blindly.
> >
> > Co-developed-by: Zeng Guang <guang.zeng@xxxxxxxxx>
> > Signed-off-by: Zeng Guang <guang.zeng@xxxxxxxxx>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> >
> > ---
> > v3: Program NMI source vector in PVTPC unconditionally (HPA)
> > v2: Fix a compile error apic_perfmon_ctr is undefined in i386 config
> > ---
> > arch/x86/events/core.c | 6 ++++--
> > arch/x86/events/intel/core.c | 6 +++---
> > arch/x86/include/asm/apic.h | 1 +
> > 3 files changed, 8 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
> > index 1ef2201e48ac..be75bdcdd400 100644
> > --- a/arch/x86/events/core.c
> > +++ b/arch/x86/events/core.c
> > @@ -46,6 +46,7 @@
> >
> > struct x86_pmu x86_pmu __read_mostly;
> > static struct pmu pmu;
> > +u32 apic_perfmon_ctr = APIC_DM_NMI;>
> > DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events) = {
> > .enabled = 1,
> > @@ -1680,7 +1681,7 @@ int x86_pmu_handle_irq(struct pt_regs *regs)
> > * This generic handler doesn't seem to have any issues where
> > the
> > * unmasking occurs so it was left at the top.
> > */
> > - apic_write(APIC_LVTPC, APIC_DM_NMI);
> > + apic_write(APIC_LVTPC, apic_perfmon_ctr);
> >
> > for (idx = 0; idx < x86_pmu.num_counters; idx++) {
> > if (!test_bit(idx, cpuc->active_mask))
> > @@ -1723,7 +1724,8 @@ void perf_events_lapic_init(void)
> > /*
> > * Always use NMI for PMU
> > */
> > - apic_write(APIC_LVTPC, APIC_DM_NMI);
> > + apic_perfmon_ctr |= NMI_SOURCE_VEC_PMI;
> > + apic_write(APIC_LVTPC, apic_perfmon_ctr);
>
>
> It looks like the same value is written unconditionally.
>
> Why not use a macro, e.g., APIC_DM_NMI_WITH_SOURCE, to replace the
> variable?
>
yes, it is unconditional now. I will use the following:
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -30,6 +30,8 @@
#define APIC_EXTNMI_ALL 1
#define APIC_EXTNMI_NONE 2
+#define APIC_PERF_NMI (APIC_DM_NMI | NMI_SOURCE_VEC_PMI)
Thanks,
Jacob