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authorH. Peter Anvin <hpa@linux.intel.com>2010-09-17 15:39:11 -0700
committerH. Peter Anvin <hpa@linux.intel.com>2010-09-17 15:39:11 -0700
commitea53069231f9317062910d6e772cca4ce93de8c8 (patch)
tree0a78cf38c59c92114473925c74a3cf86ed1e543b /arch/x86/kernel/smpboot.c
parentbc83cccc761953f878088cdfa682de0970b5561f (diff)
downloadop-kernel-dev-ea53069231f9317062910d6e772cca4ce93de8c8.zip
op-kernel-dev-ea53069231f9317062910d6e772cca4ce93de8c8.tar.gz
x86, hotplug: Use mwait to offline a processor, fix the legacy case
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>
Diffstat (limited to 'arch/x86/kernel/smpboot.c')
-rw-r--r--arch/x86/kernel/smpboot.c63
1 files changed, 62 insertions, 1 deletions
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 8b3bfc4..07bf423 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -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 */
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