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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /arch/x86/include/asm/mwait.h
Initial import
Diffstat (limited to 'arch/x86/include/asm/mwait.h')
-rw-r--r--arch/x86/include/asm/mwait.h67
1 files changed, 67 insertions, 0 deletions
diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h
new file mode 100644
index 000000000..653dfa766
--- /dev/null
+++ b/arch/x86/include/asm/mwait.h
@@ -0,0 +1,67 @@
+#ifndef _ASM_X86_MWAIT_H
+#define _ASM_X86_MWAIT_H
+
+#include <linux/sched.h>
+
+#define MWAIT_SUBSTATE_MASK 0xf
+#define MWAIT_CSTATE_MASK 0xf
+#define MWAIT_SUBSTATE_SIZE 4
+#define MWAIT_HINT2CSTATE(hint) (((hint) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK)
+#define MWAIT_HINT2SUBSTATE(hint) ((hint) & MWAIT_CSTATE_MASK)
+
+#define CPUID_MWAIT_LEAF 5
+#define CPUID5_ECX_EXTENSIONS_SUPPORTED 0x1
+#define CPUID5_ECX_INTERRUPT_BREAK 0x2
+
+#define MWAIT_ECX_INTERRUPT_BREAK 0x1
+
+static inline void __monitor(const void *eax, unsigned long ecx,
+ unsigned long edx)
+{
+ /* "monitor %eax, %ecx, %edx;" */
+ asm volatile(".byte 0x0f, 0x01, 0xc8;"
+ :: "a" (eax), "c" (ecx), "d"(edx));
+}
+
+static inline void __mwait(unsigned long eax, unsigned long ecx)
+{
+ /* "mwait %eax, %ecx;" */
+ asm volatile(".byte 0x0f, 0x01, 0xc9;"
+ :: "a" (eax), "c" (ecx));
+}
+
+static inline void __sti_mwait(unsigned long eax, unsigned long ecx)
+{
+ trace_hardirqs_on();
+ /* "mwait %eax, %ecx;" */
+ asm volatile("sti; .byte 0x0f, 0x01, 0xc9;"
+ :: "a" (eax), "c" (ecx));
+}
+
+/*
+ * This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
+ * which can obviate IPI to trigger checking of need_resched.
+ * We execute MONITOR against need_resched and enter optimized wait state
+ * through MWAIT. Whenever someone changes need_resched, we would be woken
+ * up from MWAIT (without an IPI).
+ *
+ * New with Core Duo processors, MWAIT can take some hints based on CPU
+ * capability.
+ */
+static inline void mwait_idle_with_hints(unsigned long eax, unsigned long ecx)
+{
+ if (!current_set_polling_and_test()) {
+ if (static_cpu_has_bug(X86_BUG_CLFLUSH_MONITOR)) {
+ mb();
+ clflush((void *)&current_thread_info()->flags);
+ mb();
+ }
+
+ __monitor((void *)&current_thread_info()->flags, 0, 0);
+ if (!need_resched())
+ __mwait(eax, ecx);
+ }
+ current_clr_polling();
+}
+
+#endif /* _ASM_X86_MWAIT_H */