Commit 27be4570 authored by Len Brown's avatar Len Brown
Browse files

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: default avatarLen Brown <len.brown@intel.com>
Cc: x86@kernel.org
parent 69fb3676

Documentation/kernel-parameters.txt

+0 −4
Original line number Diff line number Diff line
@@ -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.

arch/x86/include/asm/processor.h

+0 −10
Original line number Diff line number Diff line
@@ -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);

arch/x86/kernel/cpu/bugs.c

+0 −27
Original line number Diff line number Diff line
@@ -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();

arch/x86/kernel/cpu/proc.c

+0 −2
Original line number Diff line number Diff line
@@ -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",

arch/x86/kernel/process.c

+2 −4
Original line number Diff line number Diff line
@@ -415,11 +415,9 @@ void stop_this_cpu(void *dummy) 
	set_cpu_online(smp_processor_id(), false);

	disable_local_APIC();



	for (;;) {

		if (hlt_works(smp_processor_id()))

	for (;;)

		halt();

}

}



/*

 * On SMP it's slightly faster (but much more power-consuming!)

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