forked from Minki/linux
3cded41794
Avoid the pointless function call to pv_lock_ops.vcpu_is_preempted() when a paravirt spinlock enabled kernel is ran on native hardware. Do this by patching out the CALL instruction with "XOR %RAX,%RAX" which has the same effect (0 return value). Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: David.Laight@ACULAB.COM Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: benh@kernel.crashing.org Cc: boqun.feng@gmail.com Cc: borntraeger@de.ibm.com Cc: bsingharora@gmail.com Cc: dave@stgolabs.net Cc: jgross@suse.com Cc: kernellwp@gmail.com Cc: konrad.wilk@oracle.com Cc: mpe@ellerman.id.au Cc: paulmck@linux.vnet.ibm.com Cc: paulus@samba.org Cc: pbonzini@redhat.com Cc: rkrcmar@redhat.com Cc: will.deacon@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
73 lines
1.8 KiB
C
73 lines
1.8 KiB
C
#ifndef _ASM_X86_QSPINLOCK_H
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#define _ASM_X86_QSPINLOCK_H
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#include <asm/cpufeature.h>
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#include <asm-generic/qspinlock_types.h>
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#include <asm/paravirt.h>
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#define queued_spin_unlock queued_spin_unlock
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/**
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* queued_spin_unlock - release a queued spinlock
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* @lock : Pointer to queued spinlock structure
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*
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* A smp_store_release() on the least-significant byte.
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*/
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static inline void native_queued_spin_unlock(struct qspinlock *lock)
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{
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smp_store_release((u8 *)lock, 0);
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}
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#ifdef CONFIG_PARAVIRT_SPINLOCKS
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extern void native_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
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extern void __pv_init_lock_hash(void);
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extern void __pv_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
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extern void __raw_callee_save___pv_queued_spin_unlock(struct qspinlock *lock);
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static inline void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
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{
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pv_queued_spin_lock_slowpath(lock, val);
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}
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static inline void queued_spin_unlock(struct qspinlock *lock)
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{
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pv_queued_spin_unlock(lock);
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}
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#define vcpu_is_preempted vcpu_is_preempted
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static inline bool vcpu_is_preempted(int cpu)
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{
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return pv_vcpu_is_preempted(cpu);
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}
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#else
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static inline void queued_spin_unlock(struct qspinlock *lock)
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{
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native_queued_spin_unlock(lock);
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}
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#endif
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#ifdef CONFIG_PARAVIRT
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#define virt_spin_lock virt_spin_lock
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static inline bool virt_spin_lock(struct qspinlock *lock)
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{
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if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
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return false;
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/*
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* On hypervisors without PARAVIRT_SPINLOCKS support we fall
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* back to a Test-and-Set spinlock, because fair locks have
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* horrible lock 'holder' preemption issues.
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*/
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do {
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while (atomic_read(&lock->val) != 0)
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cpu_relax();
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} while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0);
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return true;
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}
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#endif /* CONFIG_PARAVIRT */
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#include <asm-generic/qspinlock.h>
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#endif /* _ASM_X86_QSPINLOCK_H */
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