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x86, hotplug: Use mwait to offline a processor, fix the legacy case

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The code in native_play_dead() has a number of problems:

1. We should use MWAIT when available, to put ourselves into a deeper
   sleep state.
2. We use the existence of CLFLUSH to determine if WBINVD is safe, but
   that is totally bogus -- WBINVD is 486+, whereas CLFLUSH is a much
   later addition.
3. We should do WBINVD inside the loop, just in case of something like
   setting an A bit on page tables.  Pointed out by Arjan van de Ven.

This code is based in part of a previous patch by Venki Pallipadi, but
unlike that patch this one keeps all the detection code local instead
of pre-caching a bunch of information.  We're shutting down the CPU;
there is absolutely no hurry.

This patch moves all the code to C and deletes the global
wbinvd_halt() which is broken anyway.

Originally-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Reviewed-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Venkatesh Pallipadi <venki@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.hl>
LKML-Reference: <20090522232230.162239000@intel.com>
This commit is contained in:
H. Peter Anvin 2010-09-17 15:39:11 -07:00
parent bc83cccc76
commit ea53069231
2 changed files with 62 additions and 24 deletions
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23
arch/x86/include/asm/processor.h
View File

@ -764,29 +764,6 @@ extern unsigned long idle_halt;
extern unsigned long idle_nomwait;
extern bool c1e_detected;
/*
* 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);

63
arch/x86/kernel/smpboot.c
View File

@ -62,6 +62,7 @@
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include <asm/mtrr.h>
#include <asm/mwait.h>
#include <asm/vmi.h>
#include <asm/apic.h>
#include <asm/setup.h>
@ -1383,11 +1384,71 @@ void play_dead_common(void)
local_irq_disable();
}
/*
* 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;
if (!cpu_has(&current_cpu_data, X86_FEATURE_MWAIT))
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);
}
while (1) {
mb();
wbinvd();
__monitor(&current_thread_info()->flags, 0, 0);
mb();
__mwait(eax, 0);
}
}
static inline void hlt_play_dead(void)
{
while (1) {
mb();
if (current_cpu_data.x86 >= 4)
wbinvd();
mb();
native_halt();
}
}
void native_play_dead(void)
{
play_dead_common();
tboot_shutdown(TB_SHUTDOWN_WFS);
wbinvd_halt();
mwait_play_dead(); /* Only returns on failure */
hlt_play_dead();
}
#else /* ... !CONFIG_HOTPLUG_CPU */