* Two x86 idle cleanups @ 2013-02-10 8:10 Len Brown 2013-02-10 8:10 ` [PATCH 1/2] x86 idle: remove mwait_idle() and "idle=mwait" cmdline param Len Brown 0 siblings, 1 reply; 6+ messages in thread From: Len Brown @ 2013-02-10 8:10 UTC (permalink / raw) To: linux-pm; +Cc: linux-kernel The following two patches remove cruft from the x86 native idle code. These two removals have been marked with a WARN() since Linux 3.0. Let me know if you see any troubles w/ these patches. TIP, These will conflict with another patch in my tree. So if you approve, please Ack and I can carry in my tree. thanks, Len Brown, Intel Open Source Technology Center ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 1/2] x86 idle: remove mwait_idle() and "idle=mwait" cmdline param 2013-02-10 8:10 Two x86 idle cleanups Len Brown @ 2013-02-10 8:10 ` Len Brown 2013-02-10 8:10 ` [PATCH 2/2] x86 idle: remove 32-bit-only "no-hlt" parameter, hlt_works_ok flag Len Brown 0 siblings, 1 reply; 6+ messages in thread From: Len Brown @ 2013-02-10 8:10 UTC (permalink / raw) To: linux-pm; +Cc: linux-kernel, Len Brown, x86 From: Len Brown <len.brown@intel.com> mwait_idle() is a C1-only idle loop intended to be more efficient than HLT, starting on Pentium-4 HT-enabled processors. But mwait_idle() has been replaced by the more general mwait_idle_with_hints(), which handles both C1 and deeper C-states. ACPI processor_idle and intel_idle use only mwait_idle_with_hints(), and no longer use mwait_idle(). Here we simplify the x86 native idle code by removing mwait_idle(), and the "idle=mwait" bootparam used to invoke it. Since Linux 3.0 there has been a boot-time warning when "idle=mwait" was invoked saying it would be removed in 2012. This removal was also noted in the (now removed:-) feature-removal-schedule.txt. After this change, kernels configured with (CONFIG_ACPI=n && CONFIG_INTEL_IDLE=n) when run on hardware that supports MWAIT will simply use HLT. If MWAIT is desired on those systems, cpuidle and the cpuidle drivers above can be enabled. Signed-off-by: Len Brown <len.brown@intel.com> Cc: x86@kernel.org --- Documentation/kernel-parameters.txt | 7 +--- arch/x86/include/asm/processor.h | 2 +- arch/x86/kernel/process.c | 79 +------------------------------------ arch/x86/kernel/smpboot.c | 2 +- drivers/acpi/processor_idle.c | 1 - 5 files changed, 4 insertions(+), 87 deletions(-) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 363e348..3b0cd1e 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1039,16 +1039,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted. Claim all unknown PCI IDE storage controllers. idle= [X86] - Format: idle=poll, idle=mwait, idle=halt, idle=nomwait + Format: idle=poll, idle=halt, idle=nomwait Poll forces a polling idle loop that can slightly improve the performance of waking up a idle CPU, but will use a lot of power and make the system run hot. Not recommended. - idle=mwait: On systems which support MONITOR/MWAIT but - the kernel chose to not use it because it doesn't save - as much power as a normal idle loop, use the - MONITOR/MWAIT idle loop anyways. Performance should be - the same as idle=poll. idle=halt: Halt is forced to be used for CPU idle. In such case C2/C3 won't be used again. idle=nomwait: Disable mwait for CPU C-states diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index c2f7f47..8a28fea 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -725,7 +725,7 @@ extern unsigned long boot_option_idle_override; extern bool amd_e400_c1e_detected; enum idle_boot_override {IDLE_NO_OVERRIDE=0, IDLE_HALT, IDLE_NOMWAIT, - IDLE_POLL, IDLE_FORCE_MWAIT}; + IDLE_POLL}; extern void enable_sep_cpu(void); extern int sysenter_setup(void); diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 7ed9f6b0..cd5a4c9 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -421,27 +421,6 @@ void stop_this_cpu(void *dummy) } } -/* Default MONITOR/MWAIT with no hints, used for default C1 state */ -static void mwait_idle(void) -{ - if (!need_resched()) { - trace_power_start_rcuidle(POWER_CSTATE, 1, smp_processor_id()); - trace_cpu_idle_rcuidle(1, smp_processor_id()); - if (this_cpu_has(X86_FEATURE_CLFLUSH_MONITOR)) - clflush((void *)¤t_thread_info()->flags); - - __monitor((void *)¤t_thread_info()->flags, 0, 0); - smp_mb(); - if (!need_resched()) - __sti_mwait(0, 0); - else - local_irq_enable(); - trace_power_end_rcuidle(smp_processor_id()); - trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id()); - } else - local_irq_enable(); -} - /* * On SMP it's slightly faster (but much more power-consuming!) * to poll the ->work.need_resched flag instead of waiting for the @@ -458,53 +437,6 @@ static void poll_idle(void) trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id()); } -/* - * mwait selection logic: - * - * It depends on the CPU. For AMD CPUs that support MWAIT this is - * wrong. Family 0x10 and 0x11 CPUs will enter C1 on HLT. Powersavings - * then depend on a clock divisor and current Pstate of the core. If - * all cores of a processor are in halt state (C1) the processor can - * enter the C1E (C1 enhanced) state. If mwait is used this will never - * happen. - * - * idle=mwait overrides this decision and forces the usage of mwait. - */ - -#define MWAIT_INFO 0x05 -#define MWAIT_ECX_EXTENDED_INFO 0x01 -#define MWAIT_EDX_C1 0xf0 - -int mwait_usable(const struct cpuinfo_x86 *c) -{ - u32 eax, ebx, ecx, edx; - - /* Use mwait if idle=mwait boot option is given */ - if (boot_option_idle_override == IDLE_FORCE_MWAIT) - return 1; - - /* - * Any idle= boot option other than idle=mwait means that we must not - * use mwait. Eg: idle=halt or idle=poll or idle=nomwait - */ - if (boot_option_idle_override != IDLE_NO_OVERRIDE) - return 0; - - if (c->cpuid_level < MWAIT_INFO) - return 0; - - cpuid(MWAIT_INFO, &eax, &ebx, &ecx, &edx); - /* Check, whether EDX has extended info about MWAIT */ - if (!(ecx & MWAIT_ECX_EXTENDED_INFO)) - return 1; - - /* - * edx enumeratios MONITOR/MWAIT extensions. Check, whether - * C1 supports MWAIT - */ - return (edx & MWAIT_EDX_C1); -} - bool amd_e400_c1e_detected; EXPORT_SYMBOL(amd_e400_c1e_detected); @@ -576,13 +508,7 @@ void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c) if (pm_idle) return; - if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) { - /* - * One CPU supports mwait => All CPUs supports mwait - */ - pr_info("using mwait in idle threads\n"); - pm_idle = mwait_idle; - } else if (cpu_has_amd_erratum(amd_erratum_400)) { + if (cpu_has_amd_erratum(amd_erratum_400)) { /* E400: APIC timer interrupt does not wake up CPU from C1e */ pr_info("using AMD E400 aware idle routine\n"); pm_idle = amd_e400_idle; @@ -606,9 +532,6 @@ static int __init idle_setup(char *str) pr_info("using polling idle threads\n"); pm_idle = poll_idle; boot_option_idle_override = IDLE_POLL; - } else if (!strcmp(str, "mwait")) { - boot_option_idle_override = IDLE_FORCE_MWAIT; - WARN_ONCE(1, "\"idle=mwait\" will be removed in 2012\n"); } else if (!strcmp(str, "halt")) { /* * When the boot option of idle=halt is added, halt is diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index ed0fe38..a6ceaed 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1369,7 +1369,7 @@ static inline void mwait_play_dead(void) void *mwait_ptr; struct cpuinfo_x86 *c = __this_cpu_ptr(&cpu_info); - if (!(this_cpu_has(X86_FEATURE_MWAIT) && mwait_usable(c))) + if (!this_cpu_has(X86_FEATURE_MWAIT)) return; if (!this_cpu_has(X86_FEATURE_CLFLSH)) return; diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index ed9a1cc..52a5e3a 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -84,7 +84,6 @@ static DEFINE_PER_CPU(struct cpuidle_device *, acpi_cpuidle_device); static int disabled_by_idle_boot_param(void) { return boot_option_idle_override == IDLE_POLL || - boot_option_idle_override == IDLE_FORCE_MWAIT || boot_option_idle_override == IDLE_HALT; } -- 1.8.1.3.535.ga923c31 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 2/2] x86 idle: remove 32-bit-only "no-hlt" parameter, hlt_works_ok flag 2013-02-10 8:10 ` [PATCH 1/2] x86 idle: remove mwait_idle() and "idle=mwait" cmdline param Len Brown @ 2013-02-10 8:10 ` Len Brown 2013-02-10 21:37 ` [PATCH 2/2 v2] " Len Brown 0 siblings, 1 reply; 6+ messages in thread From: Len Brown @ 2013-02-10 8:10 UTC (permalink / raw) To: linux-pm; +Cc: linux-kernel, Len Brown, x86 From: Len Brown <len.brown@intel.com> Remove 32-bit x86 a cmdline param "no-hlt", and the cpuinfo_x86.hlt_works_ok that it sets. If a user wants to avoid HLT, then "idle=poll" is much more useful, as it avoids invocation of HLT in idle, while "no-hlt" failed to do so. Indeed, hlt_works_ok was consulted in only 2 places. First, in /proc/cpuinfo where "hlt_bug yes" would be printed if and only if the user booted the system with "no-hlt" -- as there was no other code to set that flag. Second, it was consulted in stop_this_cpu(), which is invoked by native_machine_halt()/reboot_interrupt()/smp_stop_nmi_callback() -- all cases where the machine is being shutdown/reset. The flag was not consulted in the more frequently invoked play_dead()/hlt_play_dead() used in processor offline and suspend. Since Linux-3.0 there has been a run-time notice upon "no-hlt" invocations indicating that it would be removed in 2012. Signed-off-by: Len Brown <len.brown@intel.com> Cc: x86@kernel.org --- Documentation/kernel-parameters.txt | 4 ---- arch/x86/include/asm/processor.h | 10 ---------- arch/x86/kernel/cpu/bugs.c | 9 --------- arch/x86/kernel/cpu/proc.c | 2 -- arch/x86/kernel/process.c | 6 ++---- arch/x86/xen/setup.c | 3 --- 6 files changed, 2 insertions(+), 32 deletions(-) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 3b0cd1e..109ee45 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1881,10 +1881,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted. wfi(ARM) instruction doesn't work correctly and not to use it. This is also useful when using JTAG debugger. - no-hlt [BUGS=X86-32] Tells the kernel that the hlt - instruction doesn't work correctly and not to - use it. - no_file_caps Tells the kernel not to honor file capabilities. The only way then for a file to be executed with privilege is to be setuid root or executed by root. diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 8a28fea..b9e7d27 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -89,7 +89,6 @@ struct cpuinfo_x86 { char wp_works_ok; /* It doesn't on 386's */ /* Problems on some 486Dx4's and old 386's: */ - char hlt_works_ok; char hard_math; char rfu; char fdiv_bug; @@ -165,15 +164,6 @@ DECLARE_PER_CPU_SHARED_ALIGNED(struct cpuinfo_x86, cpu_info); extern const struct seq_operations cpuinfo_op; -static inline int hlt_works(int cpu) -{ -#ifdef CONFIG_X86_32 - return cpu_data(cpu).hlt_works_ok; -#else - return 1; -#endif -} - #define cache_line_size() (boot_cpu_data.x86_cache_alignment) extern void cpu_detect(struct cpuinfo_x86 *c); diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 92dfec9..2488be6 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -17,15 +17,6 @@ #include <asm/paravirt.h> #include <asm/alternative.h> -static int __init no_halt(char *s) -{ - WARN_ONCE(1, "\"no-hlt\" is deprecated, please use \"idle=poll\"\n"); - boot_cpu_data.hlt_works_ok = 0; - return 1; -} - -__setup("no-hlt", no_halt); - static int __init no_387(char *s) { boot_cpu_data.hard_math = 0; diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c index 3286a92..e280253 100644 --- a/arch/x86/kernel/cpu/proc.c +++ b/arch/x86/kernel/cpu/proc.c @@ -28,7 +28,6 @@ static void show_cpuinfo_misc(struct seq_file *m, struct cpuinfo_x86 *c) { seq_printf(m, "fdiv_bug\t: %s\n" - "hlt_bug\t\t: %s\n" "f00f_bug\t: %s\n" "coma_bug\t: %s\n" "fpu\t\t: %s\n" @@ -36,7 +35,6 @@ static void show_cpuinfo_misc(struct seq_file *m, struct cpuinfo_x86 *c) "cpuid level\t: %d\n" "wp\t\t: %s\n", c->fdiv_bug ? "yes" : "no", - c->hlt_works_ok ? "no" : "yes", c->f00f_bug ? "yes" : "no", c->coma_bug ? "yes" : "no", c->hard_math ? "yes" : "no", diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index cd5a4c9..aef852e 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -415,10 +415,8 @@ void stop_this_cpu(void *dummy) set_cpu_online(smp_processor_id(), false); disable_local_APIC(); - for (;;) { - if (hlt_works(smp_processor_id())) - halt(); - } + for (;;) + halt(); } /* diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c index 2b73b5c..94eac5c 100644 --- a/arch/x86/xen/setup.c +++ b/arch/x86/xen/setup.c @@ -556,9 +556,6 @@ void __init xen_arch_setup(void) COMMAND_LINE_SIZE : MAX_GUEST_CMDLINE); /* Set up idle, making sure it calls safe_halt() pvop */ -#ifdef CONFIG_X86_32 - boot_cpu_data.hlt_works_ok = 1; -#endif disable_cpuidle(); disable_cpufreq(); WARN_ON(xen_set_default_idle()); -- 1.8.1.3.535.ga923c31 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 2/2 v2] x86 idle: remove 32-bit-only "no-hlt" parameter, hlt_works_ok flag 2013-02-10 8:10 ` [PATCH 2/2] x86 idle: remove 32-bit-only "no-hlt" parameter, hlt_works_ok flag Len Brown @ 2013-02-10 21:37 ` Len Brown 2013-02-10 22:26 ` Borislav Petkov 0 siblings, 1 reply; 6+ messages in thread From: Len Brown @ 2013-02-10 21:37 UTC (permalink / raw) To: Len Brown; +Cc: linux-pm, linux-kernel, Len Brown, x86 From: Len Brown <len.brown@intel.com> Remove 32-bit x86 a cmdline param "no-hlt", and the cpuinfo_x86.hlt_works_ok that it sets. If a user wants to avoid HLT, then "idle=poll" is much more useful, as it avoids invocation of HLT in idle, while "no-hlt" failed to do so. Indeed, hlt_works_ok was consulted in only 3 places. First, in /proc/cpuinfo where "hlt_bug yes" would be printed if and only if the user booted the system with "no-hlt" -- as there was no other code to set that flag. Second, check_hlt() would not invoke halt() if "no-hlt" were on the cmdline. Third, it was consulted in stop_this_cpu(), which is invoked by native_machine_halt()/reboot_interrupt()/smp_stop_nmi_callback() -- all cases where the machine is being shutdown/reset. The flag was not consulted in the more frequently invoked play_dead()/hlt_play_dead() used in processor offline and suspend. Since Linux-3.0 there has been a run-time notice upon "no-hlt" invocations indicating that it would be removed in 2012. Signed-off-by: Len Brown <len.brown@intel.com> Cc: x86@kernel.org --- v2: remove also check_hlt() --- Documentation/kernel-parameters.txt | 4 ---- arch/x86/include/asm/processor.h | 10 ---------- arch/x86/kernel/cpu/bugs.c | 27 --------------------------- arch/x86/kernel/cpu/proc.c | 2 -- arch/x86/kernel/process.c | 6 ++---- arch/x86/xen/setup.c | 3 --- 6 files changed, 2 insertions(+), 50 deletions(-) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 3b0cd1e..109ee45 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1881,10 +1881,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted. wfi(ARM) instruction doesn't work correctly and not to use it. This is also useful when using JTAG debugger. - no-hlt [BUGS=X86-32] Tells the kernel that the hlt - instruction doesn't work correctly and not to - use it. - no_file_caps Tells the kernel not to honor file capabilities. The only way then for a file to be executed with privilege is to be setuid root or executed by root. diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 8a28fea..b9e7d27 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -89,7 +89,6 @@ struct cpuinfo_x86 { char wp_works_ok; /* It doesn't on 386's */ /* Problems on some 486Dx4's and old 386's: */ - char hlt_works_ok; char hard_math; char rfu; char fdiv_bug; @@ -165,15 +164,6 @@ DECLARE_PER_CPU_SHARED_ALIGNED(struct cpuinfo_x86, cpu_info); extern const struct seq_operations cpuinfo_op; -static inline int hlt_works(int cpu) -{ -#ifdef CONFIG_X86_32 - return cpu_data(cpu).hlt_works_ok; -#else - return 1; -#endif -} - #define cache_line_size() (boot_cpu_data.x86_cache_alignment) extern void cpu_detect(struct cpuinfo_x86 *c); diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 92dfec9..af6455e 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -17,15 +17,6 @@ #include <asm/paravirt.h> #include <asm/alternative.h> -static int __init no_halt(char *s) -{ - WARN_ONCE(1, "\"no-hlt\" is deprecated, please use \"idle=poll\"\n"); - boot_cpu_data.hlt_works_ok = 0; - return 1; -} - -__setup("no-hlt", no_halt); - static int __init no_387(char *s) { boot_cpu_data.hard_math = 0; @@ -89,23 +80,6 @@ static void __init check_fpu(void) pr_warn("Hmm, FPU with FDIV bug\n"); } -static void __init check_hlt(void) -{ - if (boot_cpu_data.x86 >= 5 || paravirt_enabled()) - return; - - pr_info("Checking 'hlt' instruction... "); - if (!boot_cpu_data.hlt_works_ok) { - pr_cont("disabled\n"); - return; - } - halt(); - halt(); - halt(); - halt(); - pr_cont("OK\n"); -} - /* * Check whether we are able to run this kernel safely on SMP. * @@ -129,7 +103,6 @@ void __init check_bugs(void) print_cpu_info(&boot_cpu_data); #endif check_config(); - check_hlt(); init_utsname()->machine[1] = '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86); alternative_instructions(); diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c index 3286a92..e280253 100644 --- a/arch/x86/kernel/cpu/proc.c +++ b/arch/x86/kernel/cpu/proc.c @@ -28,7 +28,6 @@ static void show_cpuinfo_misc(struct seq_file *m, struct cpuinfo_x86 *c) { seq_printf(m, "fdiv_bug\t: %s\n" - "hlt_bug\t\t: %s\n" "f00f_bug\t: %s\n" "coma_bug\t: %s\n" "fpu\t\t: %s\n" @@ -36,7 +35,6 @@ static void show_cpuinfo_misc(struct seq_file *m, struct cpuinfo_x86 *c) "cpuid level\t: %d\n" "wp\t\t: %s\n", c->fdiv_bug ? "yes" : "no", - c->hlt_works_ok ? "no" : "yes", c->f00f_bug ? "yes" : "no", c->coma_bug ? "yes" : "no", c->hard_math ? "yes" : "no", diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index cd5a4c9..aef852e 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -415,10 +415,8 @@ void stop_this_cpu(void *dummy) set_cpu_online(smp_processor_id(), false); disable_local_APIC(); - for (;;) { - if (hlt_works(smp_processor_id())) - halt(); - } + for (;;) + halt(); } /* diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c index 2b73b5c..94eac5c 100644 --- a/arch/x86/xen/setup.c +++ b/arch/x86/xen/setup.c @@ -556,9 +556,6 @@ void __init xen_arch_setup(void) COMMAND_LINE_SIZE : MAX_GUEST_CMDLINE); /* Set up idle, making sure it calls safe_halt() pvop */ -#ifdef CONFIG_X86_32 - boot_cpu_data.hlt_works_ok = 1; -#endif disable_cpuidle(); disable_cpufreq(); WARN_ON(xen_set_default_idle()); -- 1.8.1.3.535.ga923c31 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH 2/2 v2] x86 idle: remove 32-bit-only "no-hlt" parameter, hlt_works_ok flag 2013-02-10 21:37 ` [PATCH 2/2 v2] " Len Brown @ 2013-02-10 22:26 ` Borislav Petkov 2013-02-10 22:33 ` H. Peter Anvin 0 siblings, 1 reply; 6+ messages in thread From: Borislav Petkov @ 2013-02-10 22:26 UTC (permalink / raw) To: Len Brown; +Cc: linux-pm, linux-kernel, Len Brown, x86, H. Peter Anvin On Sun, Feb 10, 2013 at 04:37:27PM -0500, Len Brown wrote: > From: Len Brown <len.brown@intel.com> > > Remove 32-bit x86 a cmdline param "no-hlt", > and the cpuinfo_x86.hlt_works_ok that it sets. > > If a user wants to avoid HLT, then "idle=poll" > is much more useful, as it avoids invocation of HLT > in idle, while "no-hlt" failed to do so. > > Indeed, hlt_works_ok was consulted in only 3 places. > > First, in /proc/cpuinfo where "hlt_bug yes" > would be printed if and only if the user booted > the system with "no-hlt" -- as there was no other code > to set that flag. > > Second, check_hlt() would not invoke halt() if "no-hlt" > were on the cmdline. > > Third, it was consulted in stop_this_cpu(), which is invoked > by native_machine_halt()/reboot_interrupt()/smp_stop_nmi_callback() -- > all cases where the machine is being shutdown/reset. > The flag was not consulted in the more frequently invoked > play_dead()/hlt_play_dead() used in processor offline and suspend. > > Since Linux-3.0 there has been a run-time notice upon "no-hlt" invocations > indicating that it would be removed in 2012. > > Signed-off-by: Len Brown <len.brown@intel.com> > Cc: x86@kernel.org > --- > v2: remove also check_hlt() [ … ] > diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c > index 3286a92..e280253 100644 > --- a/arch/x86/kernel/cpu/proc.c > +++ b/arch/x86/kernel/cpu/proc.c > @@ -28,7 +28,6 @@ static void show_cpuinfo_misc(struct seq_file *m, struct cpuinfo_x86 *c) > { > seq_printf(m, > "fdiv_bug\t: %s\n" > - "hlt_bug\t\t: %s\n" Are we fine with changing /proc/cpuinfo output? We tend to consider it an API to userspace, judging by past experience... -- Regards/Gruss, Boris. Sent from a fat crate under my desk. Formatting is fine. -- ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 2/2 v2] x86 idle: remove 32-bit-only "no-hlt" parameter, hlt_works_ok flag 2013-02-10 22:26 ` Borislav Petkov @ 2013-02-10 22:33 ` H. Peter Anvin 0 siblings, 0 replies; 6+ messages in thread From: H. Peter Anvin @ 2013-02-10 22:33 UTC (permalink / raw) To: Borislav Petkov, Len Brown; +Cc: linux-pm, linux-kernel, Len Brown, x86 Yes... safer that way. Borislav Petkov <bp@alien8.de> wrote: >On Sun, Feb 10, 2013 at 04:37:27PM -0500, Len Brown wrote: >> From: Len Brown <len.brown@intel.com> >> >> Remove 32-bit x86 a cmdline param "no-hlt", >> and the cpuinfo_x86.hlt_works_ok that it sets. >> >> If a user wants to avoid HLT, then "idle=poll" >> is much more useful, as it avoids invocation of HLT >> in idle, while "no-hlt" failed to do so. >> >> Indeed, hlt_works_ok was consulted in only 3 places. >> >> First, in /proc/cpuinfo where "hlt_bug yes" >> would be printed if and only if the user booted >> the system with "no-hlt" -- as there was no other code >> to set that flag. >> >> Second, check_hlt() would not invoke halt() if "no-hlt" >> were on the cmdline. >> >> Third, it was consulted in stop_this_cpu(), which is invoked >> by native_machine_halt()/reboot_interrupt()/smp_stop_nmi_callback() >-- >> all cases where the machine is being shutdown/reset. >> The flag was not consulted in the more frequently invoked >> play_dead()/hlt_play_dead() used in processor offline and suspend. >> >> Since Linux-3.0 there has been a run-time notice upon "no-hlt" >invocations >> indicating that it would be removed in 2012. >> >> Signed-off-by: Len Brown <len.brown@intel.com> >> Cc: x86@kernel.org >> --- >> v2: remove also check_hlt() > >[ … ] > >> diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c >> index 3286a92..e280253 100644 >> --- a/arch/x86/kernel/cpu/proc.c >> +++ b/arch/x86/kernel/cpu/proc.c >> @@ -28,7 +28,6 @@ static void show_cpuinfo_misc(struct seq_file *m, >struct cpuinfo_x86 *c) >> { >> seq_printf(m, >> "fdiv_bug\t: %s\n" >> - "hlt_bug\t\t: %s\n" > >Are we fine with changing /proc/cpuinfo output? We tend to consider it >an API to userspace, judging by past experience... -- Sent from my mobile phone. Please excuse brevity and lack of formatting. ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2013-02-10 22:34 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2013-02-10 8:10 Two x86 idle cleanups Len Brown 2013-02-10 8:10 ` [PATCH 1/2] x86 idle: remove mwait_idle() and "idle=mwait" cmdline param Len Brown 2013-02-10 8:10 ` [PATCH 2/2] x86 idle: remove 32-bit-only "no-hlt" parameter, hlt_works_ok flag Len Brown 2013-02-10 21:37 ` [PATCH 2/2 v2] " Len Brown 2013-02-10 22:26 ` Borislav Petkov 2013-02-10 22:33 ` H. Peter Anvin
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