On Fri, Nov 8, 2024 at 2:52 PM Len Brown lenb@kernel.org wrote:
From: Len Brown len.brown@intel.com
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@vger.kernel.org # 6.11 Signed-off-by: Len Brown len.brown@intel.com
Overall
Reviewed-by: Rafael J. Wysocki rafael.j.wysocki@intel.com
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); }--