linux-kernel - [PATCH 9/9] x86 idle: delete mwait

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-id: <9797d1edfe558e20297785ce5b4e26339b74ea2c.1301550524.git.len.brown@intel.com>
Date:	Thu, 31 Mar 2011 02:03:24 -0400
From:	Len Brown <lenb@...nel.org>
To:	x86@...nel.org
Cc:	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	Len Brown <len.brown@...el.com>
Subject: [PATCH 9/9] x86 idle: delete mwait_idle()

From: Len Brown <len.brown@...el.com>

For ACPI mode, mwait_with_hints() in cstate.c is used instead of
process.c's mwait_idle().

For INTEL_IDLE mode, the mwait in intel_idle() is used instead of
process.c's mwait_idle().

So delete process.c's mwait_idle().
This will change the behaviour of SMP sysgtems that are
running !ACPI and !INTEL_IDLE kernels -- they will use
HALT instead of MWAIT.

This deletes the "idle=mwait" parameter, and thus the
boot_option_idle_override == IDLE_FORCE_MWAIT flag.

Signed-off-by: Len Brown <len.brown@...el.com>
---
 Documentation/kernel-parameters.txt |    7 +------
 arch/x86/include/asm/processor.h    |    2 +-
 arch/x86/kernel/process.c           |   34 +---------------------------------
 drivers/acpi/processor_idle.c       |    1 -
 4 files changed, 3 insertions(+), 41 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index e6b4843..ce9624a 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -917,16 +917,11 @@ 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 3b288ca..0d8d2a4 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -752,7 +752,7 @@ extern unsigned long		boot_option_idle_override;
 extern bool			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 9f08e7b..4b93d50 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -399,27 +399,6 @@ void cpu_idle_wait(void)
 }
 EXPORT_SYMBOL_GPL(cpu_idle_wait);
 
-/* Default MONITOR/MWAIT with no hints, used for default C1 state */
-static void mwait_idle(void)
-{
-	if (!need_resched()) {
-		trace_power_start(POWER_CSTATE, 1, smp_processor_id());
-		trace_cpu_idle(1, smp_processor_id());
-		if (cpu_has(__this_cpu_ptr(&cpu_info), X86_FEATURE_CLFLUSH_MONITOR))
-			clflush((void *)&current_thread_info()->flags);
-
-		__monitor((void *)&current_thread_info()->flags, 0, 0);
-		smp_mb();
-		if (!need_resched())
-			__sti_mwait(0, 0);
-		else
-			local_irq_enable();
-		trace_power_end(smp_processor_id());
-		trace_cpu_idle(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
@@ -457,9 +436,6 @@ int mwait_usable(const struct cpuinfo_x86 *c)
 {
 	u32 eax, ebx, ecx, edx;
 
-	if (boot_option_idle_override == IDLE_FORCE_MWAIT)
-		return 1;
-
 	if (c->cpuid_level < MWAIT_INFO)
 		return 0;
 
@@ -548,13 +524,7 @@ 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
-		 */
-		printk(KERN_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 */
 		printk(KERN_INFO "using C1E aware idle routine\n");
 		pm_idle = c1e_idle;
@@ -578,8 +548,6 @@ static int __init idle_setup(char *str)
 		printk("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;
 	} else if (!strcmp(str, "halt")) {
 		/*
 		 * When the boot option of idle=halt is added, halt is
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index d615b7d..a15390c 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -82,7 +82,6 @@ module_param(latency_factor, uint, 0644);
 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;
 }
 
-- 
1.7.4.2.406.gbe91

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/