From 570bd39ac8505e57b1d62e56b84eea9de8473c15 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Tue, 30 Aug 2011 15:35:11 -0700 Subject: [PATCH] Revert "x86, hotplug: Use mwait to offline a processor, fix the legacy case" This reverts commit 226917b0735f31cf5c704e07fdd590d99bbfae58 (upstream ea53069231f9317062910d6e772cca4ce93de8c8 and a68e5c94f7d3dd64fef34dd5d97e365cae4bb42a and ce5f68246bf2385d6174856708d0b746dc378f20 all mushed together) as Jonathan Nieder reports that this causes a regression on some hardware. More details can be found at http://bugs.debian.org/622259 Cc: Jonathan Nieder Cc: H. Peter Anvin Cc: Len Brown Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/processor.h | 23 +++++++++ arch/x86/kernel/smpboot.c | 85 +------------------------------- 2 files changed, 24 insertions(+), 84 deletions(-) diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index da35a70f6129..fa04deade0a6 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -765,6 +765,29 @@ extern unsigned long boot_option_idle_override; extern unsigned long idle_halt; extern unsigned long idle_nomwait; +/* + * on systems with caches, caches must be flashed as the absolute + * last instruction before going into a suspended halt. Otherwise, + * dirty data can linger in the cache and become stale on resume, + * leading to strange errors. + * + * perform a variety of operations to guarantee that the compiler + * will not reorder instructions. wbinvd itself is serializing + * so the processor will not reorder. + * + * Systems without cache can just go into halt. + */ +static inline void wbinvd_halt(void) +{ + mb(); + /* check for clflush to determine if wbinvd is legal */ + if (cpu_has_clflush) + asm volatile("cli; wbinvd; 1: hlt; jmp 1b" : : : "memory"); + else + while (1) + halt(); +} + extern void enable_sep_cpu(void); extern int sysenter_setup(void); diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 539bb6cacf54..7e8e905e2ccb 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1338,94 +1338,11 @@ void play_dead_common(void) local_irq_disable(); } -#define MWAIT_SUBSTATE_MASK 0xf -#define MWAIT_SUBSTATE_SIZE 4 - -#define CPUID_MWAIT_LEAF 5 -#define CPUID5_ECX_EXTENSIONS_SUPPORTED 0x1 - -/* - * We need to flush the caches before going to sleep, lest we have - * dirty data in our caches when we come back up. - */ -static inline void mwait_play_dead(void) -{ - unsigned int eax, ebx, ecx, edx; - unsigned int highest_cstate = 0; - unsigned int highest_subcstate = 0; - int i; - void *mwait_ptr; - - if (!cpu_has(¤t_cpu_data, X86_FEATURE_MWAIT)) - return; - if (!cpu_has(¤t_cpu_data, X86_FEATURE_CLFLSH)) - return; - if (current_cpu_data.cpuid_level < CPUID_MWAIT_LEAF) - return; - - eax = CPUID_MWAIT_LEAF; - ecx = 0; - native_cpuid(&eax, &ebx, &ecx, &edx); - - /* - * eax will be 0 if EDX enumeration is not valid. - * Initialized below to cstate, sub_cstate value when EDX is valid. - */ - if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED)) { - eax = 0; - } else { - edx >>= MWAIT_SUBSTATE_SIZE; - for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) { - if (edx & MWAIT_SUBSTATE_MASK) { - highest_cstate = i; - highest_subcstate = edx & MWAIT_SUBSTATE_MASK; - } - } - eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) | - (highest_subcstate - 1); - } - - /* - * This should be a memory location in a cache line which is - * unlikely to be touched by other processors. The actual - * content is immaterial as it is not actually modified in any way. - */ - mwait_ptr = ¤t_thread_info()->flags; - - wbinvd(); - - while (1) { - /* - * The CLFLUSH is a workaround for erratum AAI65 for - * the Xeon 7400 series. It's not clear it is actually - * needed, but it should be harmless in either case. - * The WBINVD is insufficient due to the spurious-wakeup - * case where we return around the loop. - */ - clflush(mwait_ptr); - __monitor(mwait_ptr, 0, 0); - mb(); - __mwait(eax, 0); - } -} - -static inline void hlt_play_dead(void) -{ - if (current_cpu_data.x86 >= 4) - wbinvd(); - - while (1) { - native_halt(); - } -} - void native_play_dead(void) { play_dead_common(); tboot_shutdown(TB_SHUTDOWN_WFS); - - mwait_play_dead(); /* Only returns on failure */ - hlt_play_dead(); + wbinvd_halt(); } #else /* ... !CONFIG_HOTPLUG_CPU */ -- 2.39.5