forked from Minki/linux
08e237fa56
Monitored cached line may not wake up from mwait on certain Goldmont based CPUs. This patch will avoid calling current_set_polling_and_test() and thereby not set the TIF_ flag. The result is that we'll always send IPIs for wakeups. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Len Brown <lenb@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1468867270-18493-1-git-send-email-jacob.jun.pan@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
115 lines
3.5 KiB
C
115 lines
3.5 KiB
C
#ifndef _ASM_X86_MWAIT_H
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#define _ASM_X86_MWAIT_H
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#include <linux/sched.h>
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#include <asm/cpufeature.h>
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#define MWAIT_SUBSTATE_MASK 0xf
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#define MWAIT_CSTATE_MASK 0xf
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#define MWAIT_SUBSTATE_SIZE 4
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#define MWAIT_HINT2CSTATE(hint) (((hint) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK)
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#define MWAIT_HINT2SUBSTATE(hint) ((hint) & MWAIT_CSTATE_MASK)
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#define CPUID_MWAIT_LEAF 5
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#define CPUID5_ECX_EXTENSIONS_SUPPORTED 0x1
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#define CPUID5_ECX_INTERRUPT_BREAK 0x2
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#define MWAIT_ECX_INTERRUPT_BREAK 0x1
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#define MWAITX_ECX_TIMER_ENABLE BIT(1)
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#define MWAITX_MAX_LOOPS ((u32)-1)
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#define MWAITX_DISABLE_CSTATES 0xf
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static inline void __monitor(const void *eax, unsigned long ecx,
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unsigned long edx)
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{
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/* "monitor %eax, %ecx, %edx;" */
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asm volatile(".byte 0x0f, 0x01, 0xc8;"
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:: "a" (eax), "c" (ecx), "d"(edx));
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}
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static inline void __monitorx(const void *eax, unsigned long ecx,
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unsigned long edx)
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{
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/* "monitorx %eax, %ecx, %edx;" */
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asm volatile(".byte 0x0f, 0x01, 0xfa;"
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:: "a" (eax), "c" (ecx), "d"(edx));
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}
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static inline void __mwait(unsigned long eax, unsigned long ecx)
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{
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/* "mwait %eax, %ecx;" */
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asm volatile(".byte 0x0f, 0x01, 0xc9;"
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:: "a" (eax), "c" (ecx));
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}
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/*
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* MWAITX allows for a timer expiration to get the core out a wait state in
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* addition to the default MWAIT exit condition of a store appearing at a
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* monitored virtual address.
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*
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* Registers:
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*
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* MWAITX ECX[1]: enable timer if set
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* MWAITX EBX[31:0]: max wait time expressed in SW P0 clocks. The software P0
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* frequency is the same as the TSC frequency.
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*
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* Below is a comparison between MWAIT and MWAITX on AMD processors:
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*
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* MWAIT MWAITX
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* opcode 0f 01 c9 | 0f 01 fb
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* ECX[0] value of RFLAGS.IF seen by instruction
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* ECX[1] unused/#GP if set | enable timer if set
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* ECX[31:2] unused/#GP if set
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* EAX unused (reserve for hint)
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* EBX[31:0] unused | max wait time (P0 clocks)
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*
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* MONITOR MONITORX
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* opcode 0f 01 c8 | 0f 01 fa
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* EAX (logical) address to monitor
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* ECX #GP if not zero
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*/
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static inline void __mwaitx(unsigned long eax, unsigned long ebx,
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unsigned long ecx)
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{
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/* "mwaitx %eax, %ebx, %ecx;" */
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asm volatile(".byte 0x0f, 0x01, 0xfb;"
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:: "a" (eax), "b" (ebx), "c" (ecx));
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}
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static inline void __sti_mwait(unsigned long eax, unsigned long ecx)
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{
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trace_hardirqs_on();
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/* "mwait %eax, %ecx;" */
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asm volatile("sti; .byte 0x0f, 0x01, 0xc9;"
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:: "a" (eax), "c" (ecx));
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}
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/*
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* This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
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* which can obviate IPI to trigger checking of need_resched.
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* We execute MONITOR against need_resched and enter optimized wait state
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* through MWAIT. Whenever someone changes need_resched, we would be woken
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* up from MWAIT (without an IPI).
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*
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* New with Core Duo processors, MWAIT can take some hints based on CPU
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* capability.
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*/
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static inline void mwait_idle_with_hints(unsigned long eax, unsigned long ecx)
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{
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if (static_cpu_has_bug(X86_BUG_MONITOR) || !current_set_polling_and_test()) {
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if (static_cpu_has_bug(X86_BUG_CLFLUSH_MONITOR)) {
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mb();
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clflush((void *)¤t_thread_info()->flags);
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mb();
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}
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__monitor((void *)¤t_thread_info()->flags, 0, 0);
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if (!need_resched())
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__mwait(eax, ecx);
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}
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current_clr_polling();
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}
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#endif /* _ASM_X86_MWAIT_H */
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