From a7dd183f0b3848c056bbeed78ef5d5c52fe94d83 Mon Sep 17 00:00:00 2001 From: Patryk Wlazlyn Date: Wed, 5 Feb 2025 17:52:08 +0200 Subject: [PATCH] x86/smp: Allow calling mwait_play_dead with an arbitrary hint Introduce a helper function to allow offlined CPUs to enter idle states with a specific MWAIT hint. The new helper will be used in subsequent patches by the acpi_idle and intel_idle drivers. No functional change intended. Signed-off-by: Patryk Wlazlyn Signed-off-by: Artem Bityutskiy Signed-off-by: Dave Hansen Reviewed-by: Gautham R. Shenoy Acked-by: Rafael J. Wysocki Link: https://lore.kernel.org/all/20250205155211.329780-2-artem.bityutskiy%40linux.intel.com --- arch/x86/include/asm/smp.h | 3 ++ arch/x86/kernel/smpboot.c | 88 ++++++++++++++++++++------------------ 2 files changed, 50 insertions(+), 41 deletions(-) diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h index ca073f40698fa..80f8bfd83fc7b 100644 --- a/arch/x86/include/asm/smp.h +++ b/arch/x86/include/asm/smp.h @@ -114,6 +114,7 @@ void wbinvd_on_cpu(int cpu); int wbinvd_on_all_cpus(void); void smp_kick_mwait_play_dead(void); +void mwait_play_dead(unsigned int eax_hint); void native_smp_send_reschedule(int cpu); void native_send_call_func_ipi(const struct cpumask *mask); @@ -164,6 +165,8 @@ static inline struct cpumask *cpu_llc_shared_mask(int cpu) { return (struct cpumask *)cpumask_of(0); } + +static inline void mwait_play_dead(unsigned int eax_hint) { } #endif /* CONFIG_SMP */ #ifdef CONFIG_DEBUG_NMI_SELFTEST diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index c10850ae6f094..8aad14e43f549 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1258,47 +1258,9 @@ void play_dead_common(void) local_irq_disable(); } -/* - * We need to flush the caches before going to sleep, lest we have - * dirty data in our caches when we come back up. - */ -static inline void mwait_play_dead(void) +void __noreturn mwait_play_dead(unsigned int eax_hint) { struct mwait_cpu_dead *md = this_cpu_ptr(&mwait_cpu_dead); - unsigned int eax, ebx, ecx, edx; - unsigned int highest_cstate = 0; - unsigned int highest_subcstate = 0; - int i; - - if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || - boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) - return; - if (!this_cpu_has(X86_FEATURE_MWAIT)) - return; - if (!this_cpu_has(X86_FEATURE_CLFLUSH)) - return; - - eax = CPUID_LEAF_MWAIT; - ecx = 0; - native_cpuid(&eax, &ebx, &ecx, &edx); - - /* - * eax will be 0 if EDX enumeration is not valid. - * Initialized below to cstate, sub_cstate value when EDX is valid. - */ - if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED)) { - eax = 0; - } else { - edx >>= MWAIT_SUBSTATE_SIZE; - for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) { - if (edx & MWAIT_SUBSTATE_MASK) { - highest_cstate = i; - highest_subcstate = edx & MWAIT_SUBSTATE_MASK; - } - } - eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) | - (highest_subcstate - 1); - } /* Set up state for the kexec() hack below */ md->status = CPUDEAD_MWAIT_WAIT; @@ -1319,7 +1281,7 @@ static inline void mwait_play_dead(void) mb(); __monitor(md, 0, 0); mb(); - __mwait(eax, 0); + __mwait(eax_hint, 0); if (READ_ONCE(md->control) == CPUDEAD_MWAIT_KEXEC_HLT) { /* @@ -1341,6 +1303,50 @@ static inline void mwait_play_dead(void) } } +/* + * We need to flush the caches before going to sleep, lest we have + * dirty data in our caches when we come back up. + */ +static inline void mwait_play_dead_cpuid_hint(void) +{ + unsigned int eax, ebx, ecx, edx; + unsigned int highest_cstate = 0; + unsigned int highest_subcstate = 0; + int i; + + if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || + boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) + return; + if (!this_cpu_has(X86_FEATURE_MWAIT)) + return; + if (!this_cpu_has(X86_FEATURE_CLFLUSH)) + return; + + eax = CPUID_LEAF_MWAIT; + ecx = 0; + native_cpuid(&eax, &ebx, &ecx, &edx); + + /* + * eax will be 0 if EDX enumeration is not valid. + * Initialized below to cstate, sub_cstate value when EDX is valid. + */ + if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED)) { + eax = 0; + } else { + edx >>= MWAIT_SUBSTATE_SIZE; + for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) { + if (edx & MWAIT_SUBSTATE_MASK) { + highest_cstate = i; + highest_subcstate = edx & MWAIT_SUBSTATE_MASK; + } + } + eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) | + (highest_subcstate - 1); + } + + mwait_play_dead(eax); +} + /* * Kick all "offline" CPUs out of mwait on kexec(). See comment in * mwait_play_dead(). @@ -1391,7 +1397,7 @@ void native_play_dead(void) play_dead_common(); tboot_shutdown(TB_SHUTDOWN_WFS); - mwait_play_dead(); + mwait_play_dead_cpuid_hint(); if (cpuidle_play_dead()) hlt_play_dead(); }