/* SPDX-License-Identifier: GPL-2.0-or-later */
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#ifndef _ASM_POWERPC_PARAVIRT_H
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#define _ASM_POWERPC_PARAVIRT_H
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#include <linux/jump_label.h>
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#include <asm/smp.h>
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#ifdef CONFIG_PPC64
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#include <asm/paca.h>
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#include <asm/lppaca.h>
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#include <asm/hvcall.h>
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#endif
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#ifdef CONFIG_PPC_SPLPAR
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DECLARE_STATIC_KEY_FALSE(shared_processor);
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static inline bool is_shared_processor(void)
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{
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return static_branch_unlikely(&shared_processor);
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}
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/* If bit 0 is set, the cpu has been preempted */
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static inline u32 yield_count_of(int cpu)
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{
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__be32 yield_count = READ_ONCE(lppaca_of(cpu).yield_count);
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return be32_to_cpu(yield_count);
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}
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/*
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* Spinlock code confers and prods, so don't trace the hcalls because the
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* tracing code takes spinlocks which can cause recursion deadlocks.
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*
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* These calls are made while the lock is not held: the lock slowpath yields if
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* it can not acquire the lock, and unlock slow path might prod if a waiter has
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* yielded). So this may not be a problem for simple spin locks because the
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* tracing does not technically recurse on the lock, but we avoid it anyway.
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*
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* However the queued spin lock contended path is more strictly ordered: the
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* H_CONFER hcall is made after the task has queued itself on the lock, so then
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* recursing on that lock will cause the task to then queue up again behind the
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* first instance (or worse: queued spinlocks use tricks that assume a context
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* never waits on more than one spinlock, so such recursion may cause random
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* corruption in the lock code).
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*/
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static inline void yield_to_preempted(int cpu, u32 yield_count)
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{
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plpar_hcall_norets_notrace(H_CONFER, get_hard_smp_processor_id(cpu), yield_count);
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}
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static inline void prod_cpu(int cpu)
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{
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plpar_hcall_norets_notrace(H_PROD, get_hard_smp_processor_id(cpu));
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}
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static inline void yield_to_any(void)
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{
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plpar_hcall_norets_notrace(H_CONFER, -1, 0);
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}
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#else
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static inline bool is_shared_processor(void)
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{
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return false;
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}
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static inline u32 yield_count_of(int cpu)
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{
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return 0;
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}
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extern void ___bad_yield_to_preempted(void);
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static inline void yield_to_preempted(int cpu, u32 yield_count)
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{
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___bad_yield_to_preempted(); /* This would be a bug */
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}
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extern void ___bad_yield_to_any(void);
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static inline void yield_to_any(void)
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{
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___bad_yield_to_any(); /* This would be a bug */
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}
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extern void ___bad_prod_cpu(void);
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static inline void prod_cpu(int cpu)
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{
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___bad_prod_cpu(); /* This would be a bug */
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}
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#endif
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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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if (!is_shared_processor())
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return false;
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if (yield_count_of(cpu) & 1)
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return true;
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return false;
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}
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static inline bool pv_is_native_spin_unlock(void)
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{
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return !is_shared_processor();
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}
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#endif /* _ASM_POWERPC_PARAVIRT_H */
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