+++ /dev/null
-From b253149b843f89cd300cbdbea27ce1f847506f99 Mon Sep 17 00:00:00 2001
-From: Len Brown <len.brown@intel.com>
-Date: Wed, 15 Jan 2014 00:37:34 -0500
-Subject: sched/idle/x86: Restore mwait_idle() to fix boot hangs, to improve power savings and to improve performance
-
-From: Len Brown <len.brown@intel.com>
-
-commit b253149b843f89cd300cbdbea27ce1f847506f99 upstream.
-
-In Linux-3.9 we removed the mwait_idle() loop:
-
- 69fb3676df33 ("x86 idle: remove mwait_idle() and "idle=mwait" cmdline param")
-
-The reasoning was that modern machines should be sufficiently
-happy during the boot process using the default_idle() HALT
-loop, until cpuidle loads and either acpi_idle or intel_idle
-invoke the newer MWAIT-with-hints idle loop.
-
-But two machines reported problems:
-
- 1. Certain Core2-era machines support MWAIT-C1 and HALT only.
- MWAIT-C1 is preferred for optimal power and performance.
- But if they support just C1, cpuidle never loads and
- so they use the boot-time default idle loop forever.
-
- 2. Some laptops will boot-hang if HALT is used,
- but will boot successfully if MWAIT is used.
- This appears to be a hidden assumption in BIOS SMI,
- that is presumably valid on the proprietary OS
- where the BIOS was validated.
-
- https://bugzilla.kernel.org/show_bug.cgi?id=60770
-
-So here we effectively revert the patch above, restoring
-the mwait_idle() loop. However, we don't bother restoring
-the idle=mwait cmdline parameter, since it appears to add
-no value.
-
-Maintainer notes:
-
- For 3.9, simply revert 69fb3676df
- for 3.10, patch -F3 applies, fuzz needed due to __cpuinit use in
- context For 3.11, 3.12, 3.13, this patch applies cleanly
-
-Tested-by: Mike Galbraith <bitbucket@online.de>
-Signed-off-by: Len Brown <len.brown@intel.com>
-Acked-by: Mike Galbraith <bitbucket@online.de>
-Cc: <stable@vger.kernel.org> # 3.9+
-Cc: Borislav Petkov <bp@alien8.de>
-Cc: H. Peter Anvin <hpa@zytor.com>
-Cc: Ian Malone <ibmalone@gmail.com>
-Cc: Josh Boyer <jwboyer@redhat.com>
-Cc: Linus Torvalds <torvalds@linux-foundation.org>
-Cc: Mike Galbraith <efault@gmx.de>
-Cc: Peter Zijlstra <peterz@infradead.org>
-Cc: Thomas Gleixner <tglx@linutronix.de>
-Link: http://lkml.kernel.org/r/345254a551eb5a6a866e048d7ab570fd2193aca4.1389763084.git.len.brown@intel.com
-[ Ported to recent kernels. ]
-[ Mike: 3.10 backport ]
-Signed-off-by: Ingo Molnar <mingo@kernel.org>
-Signed-off-by: Mike Galbraith <efault@gmx.de>
-Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
----
- arch/x86/kernel/process.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++
- 1 file changed, 49 insertions(+)
-
---- a/arch/x86/kernel/process.c
-+++ b/arch/x86/kernel/process.c
-@@ -398,6 +398,52 @@ static void amd_e400_idle(void)
- default_idle();
- }
-
-+/*
-+ * Intel Core2 and older machines prefer MWAIT over HALT for C1.
-+ * We can't rely on cpuidle installing MWAIT, because it will not load
-+ * on systems that support only C1 -- so the boot default must be MWAIT.
-+ *
-+ * Some AMD machines are the opposite, they depend on using HALT.
-+ *
-+ * So for default C1, which is used during boot until cpuidle loads,
-+ * use MWAIT-C1 on Intel HW that has it, else use HALT.
-+ */
-+static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c)
-+{
-+ if (c->x86_vendor != X86_VENDOR_INTEL)
-+ return 0;
-+
-+ if (!cpu_has(c, X86_FEATURE_MWAIT))
-+ return 0;
-+
-+ return 1;
-+}
-+
-+/*
-+ * MONITOR/MWAIT with no hints, used for default default C1 state.
-+ * This invokes MWAIT with interrutps enabled and no flags,
-+ * which is backwards compatible with the original MWAIT implementation.
-+ */
-+
-+static void mwait_idle(void)
-+{
-+ if (!current_set_polling_and_test()) {
-+ if (static_cpu_has(X86_FEATURE_CLFLUSH_MONITOR)) {
-+ mb();
-+ clflush((void *)¤t_thread_info()->flags);
-+ mb();
-+ }
-+
-+ __monitor((void *)¤t_thread_info()->flags, 0, 0);
-+ if (!need_resched())
-+ __sti_mwait(0, 0);
-+ else
-+ local_irq_enable();
-+ } else
-+ local_irq_enable();
-+ __current_clr_polling();
-+}
-+
- void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
- {
- #ifdef CONFIG_SMP
-@@ -411,6 +457,9 @@ void __cpuinit select_idle_routine(const
- /* E400: APIC timer interrupt does not wake up CPU from C1e */
- pr_info("using AMD E400 aware idle routine\n");
- x86_idle = amd_e400_idle;
-+ } else if (prefer_mwait_c1_over_halt(c)) {
-+ pr_info("using mwait in idle threads\n");
-+ x86_idle = mwait_idle;
- } else
- x86_idle = default_idle;
- }
projects / thirdparty / kernel / stable-queue.git / commitdiff
