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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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20c0e8269e
This implements the generic paravirt qspinlocks using H_PROD and H_CONFER to kick and wait. This uses an un-directed yield to any CPU rather than the directed yield to a pre-empted lock holder that paravirtualised simple spinlocks use, that requires no kick hcall. This is something that could be investigated and improved in future. Performance results can be found in the commit which added queued spinlocks. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Waiman Long <longman@redhat.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20200724131423.1362108-5-npiggin@gmail.com
88 lines
1.8 KiB
C
88 lines
1.8 KiB
C
/* 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/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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static inline void yield_to_preempted(int cpu, u32 yield_count)
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{
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plpar_hcall_norets(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(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(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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