On Fri, Nov 8, 2024 at 2:52 PM Len Brown <lenb@xxxxxxxxxx> wrote: > > From: Len Brown <len.brown@xxxxxxxxx> > > Under some conditions, MONITOR wakeups on Lunar Lake processors > can be lost, resulting in significant user-visible delays. > > Add LunarLake to X86_BUG_MONITOR so that wake_up_idle_cpu() > always sends an IPI, avoiding this potential delay. > > Also update the X86_BUG_MONITOR workaround to handle > the new smp_kick_mwait_play_dead() path. > > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219364 > > Cc: stable@xxxxxxxxxxxxxxx # 6.11 > Signed-off-by: Len Brown <len.brown@xxxxxxxxx> Overall Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > --- > arch/x86/kernel/cpu/intel.c | 3 ++- > arch/x86/kernel/smpboot.c | 3 +++ > 2 files changed, 5 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c > index e7656cbef68d..aa63f5f780a0 100644 > --- a/arch/x86/kernel/cpu/intel.c > +++ b/arch/x86/kernel/cpu/intel.c > @@ -586,7 +586,8 @@ static void init_intel(struct cpuinfo_x86 *c) > c->x86_vfm == INTEL_WESTMERE_EX)) > set_cpu_bug(c, X86_BUG_CLFLUSH_MONITOR); > > - if (boot_cpu_has(X86_FEATURE_MWAIT) && c->x86_vfm == INTEL_ATOM_GOLDMONT) > + if (boot_cpu_has(X86_FEATURE_MWAIT) && > + (c->x86_vfm == INTEL_ATOM_GOLDMONT || c->x86_vfm == INTEL_LUNARLAKE_M)) > set_cpu_bug(c, X86_BUG_MONITOR); > > #ifdef CONFIG_X86_64 > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c > index 766f092dab80..910cb2d72c13 100644 > --- a/arch/x86/kernel/smpboot.c > +++ b/arch/x86/kernel/smpboot.c > @@ -1377,6 +1377,9 @@ void smp_kick_mwait_play_dead(void) > for (i = 0; READ_ONCE(md->status) != newstate && i < 1000; i++) { > /* Bring it out of mwait */ > WRITE_ONCE(md->control, newstate); > + /* If MONITOR unreliable, send IPI */ > + if (boot_cpu_has_bug(X86_BUG_MONITOR)) > + __apic_send_IPI(cpu, RESCHEDULE_VECTOR); The __apic_send_IPI() call could be wrapped into something like __native_smp_send_reschedule() to underline the analogy between this and what happens in native_smp_send_reschedule(). It is still fine as is though IMV. > udelay(5); > } > > --
