From 69fb3676df3329a7142803bb3502fa59dc0db2e3 Mon Sep 17 00:00:00 2001 From: Len Brown Date: Sun, 10 Feb 2013 01:38:39 -0500 Subject: x86 idle: remove mwait_idle() and "idle=mwait" cmdline param 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 But mwait_idle() has been replaced by the more general mwait_idle_with_hints(), which handles both C1 and deeper C-states.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 Cc: x86@kernel.org --- Documentation/kernel-parameters.txt | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) (limited to 'Documentation/kernel-parameters.txt') diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 363e348bff9b..3b0cd1e612da 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 -- cgit v1.2.3 From 27be457000211a6903968dfce06d5f73f051a217 Mon Sep 17 00:00:00 2001 From: Len Brown Date: Sun, 10 Feb 2013 02:28:46 -0500 Subject: x86 idle: remove 32-bit-only "no-hlt" parameter, hlt_works_ok flag 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 Cc: x86@kernel.org --- 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(-) (limited to 'Documentation/kernel-parameters.txt') diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 3b0cd1e612da..109ee45cf20d 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 8a28feae1c92..b9e7d279f8ef 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 92dfec986a48..af6455e3fcc9 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -17,15 +17,6 @@ #include #include -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 3286a92e662a..e280253f6f94 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 cd5a4c9ef835..aef852eac292 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 2b73b5c8555f..94eac5c85cdc 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()); -- cgit v1.2.3