/* SPDX-License-Identifier: GPL-2.0-or-later */ #ifndef _ASM_POWERPC_PARAVIRT_H #define _ASM_POWERPC_PARAVIRT_H #include <linux/jump_label.h> #include <asm/smp.h> #ifdef CONFIG_PPC64 #include <asm/paca.h> #include <asm/lppaca.h> #include <asm/hvcall.h> #endif #ifdef CONFIG_PPC_SPLPAR #include <linux/smp.h> #include <asm/kvm_guest.h> #include <asm/cputhreads.h> DECLARE_STATIC_KEY_FALSE(shared_processor); static inline bool is_shared_processor(void) { return static_branch_unlikely(&shared_processor); } #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING u64 pseries_paravirt_steal_clock(int cpu); static inline u64 paravirt_steal_clock(int cpu) { return pseries_paravirt_steal_clock(cpu); } #endif /* If bit 0 is set, the cpu has been ceded, conferred, or preempted */ static inline u32 yield_count_of(int cpu) { __be32 yield_count = READ_ONCE(lppaca_of(cpu).yield_count); return be32_to_cpu(yield_count); } /* * Spinlock code confers and prods, so don't trace the hcalls because the * tracing code takes spinlocks which can cause recursion deadlocks. * * These calls are made while the lock is not held: the lock slowpath yields if * it can not acquire the lock, and unlock slow path might prod if a waiter has * yielded). So this may not be a problem for simple spin locks because the * tracing does not technically recurse on the lock, but we avoid it anyway. * * However the queued spin lock contended path is more strictly ordered: the * H_CONFER hcall is made after the task has queued itself on the lock, so then * recursing on that lock will cause the task to then queue up again behind the * first instance (or worse: queued spinlocks use tricks that assume a context * never waits on more than one spinlock, so such recursion may cause random * corruption in the lock code). */ static inline void yield_to_preempted(int cpu, u32 yield_count) { plpar_hcall_norets_notrace(H_CONFER, get_hard_smp_processor_id(cpu), yield_count); } static inline void prod_cpu(int cpu) { plpar_hcall_norets_notrace(H_PROD, get_hard_smp_processor_id(cpu)); } static inline void yield_to_any(void) { plpar_hcall_norets_notrace(H_CONFER, -1, 0); } static inline bool is_vcpu_idle(int vcpu) { return lppaca_of(vcpu).idle; } static inline bool vcpu_is_dispatched(int vcpu) { /* * This is the yield_count. An "odd" value (low bit on) means that * the processor is yielded (either because of an OS yield or a * hypervisor preempt). An even value implies that the processor is * currently executing. */ return (!(yield_count_of(vcpu) & 1)); } #else static inline bool is_shared_processor(void) { return false; } static inline u32 yield_count_of(int cpu) { return 0; } extern void ___bad_yield_to_preempted(void); static inline void yield_to_preempted(int cpu, u32 yield_count) { ___bad_yield_to_preempted(); /* This would be a bug */ } extern void ___bad_yield_to_any(void); static inline void yield_to_any(void) { ___bad_yield_to_any(); /* This would be a bug */ } extern void ___bad_prod_cpu(void); static inline void prod_cpu(int cpu) { ___bad_prod_cpu(); /* This would be a bug */ } static inline bool is_vcpu_idle(int vcpu) { return false; } static inline bool vcpu_is_dispatched(int vcpu) { return true; } #endif #define vcpu_is_preempted vcpu_is_preempted static inline bool vcpu_is_preempted(int cpu) { /* * The dispatch/yield bit alone is an imperfect indicator of * whether the hypervisor has dispatched @cpu to run on a physical * processor. When it is clear, @cpu is definitely not preempted. * But when it is set, it means only that it *might* be, subject to * other conditions. So we check other properties of the VM and * @cpu first, resorting to the yield count last. */ /* * Hypervisor preemption isn't possible in dedicated processor * mode by definition. */ if (!is_shared_processor()) return false; /* * If the hypervisor has dispatched the target CPU on a physical * processor, then the target CPU is definitely not preempted. */ if (vcpu_is_dispatched(cpu)) return false; /* * if the target CPU is not dispatched and the guest OS * has not marked the CPU idle, then it is hypervisor preempted. */ if (!is_vcpu_idle(cpu)) return true; #ifdef CONFIG_PPC_SPLPAR if (!is_kvm_guest()) { int first_cpu, i; /* * The result of vcpu_is_preempted() is used in a * speculative way, and is always subject to invalidation * by events internal and external to Linux. While we can * be called in preemptable context (in the Linux sense), * we're not accessing per-cpu resources in a way that can * race destructively with Linux scheduler preemption and * migration, and callers can tolerate the potential for * error introduced by sampling the CPU index without * pinning the task to it. So it is permissible to use * raw_smp_processor_id() here to defeat the preempt debug * warnings that can arise from using smp_processor_id() * in arbitrary contexts. */ first_cpu = cpu_first_thread_sibling(raw_smp_processor_id()); /* * The PowerVM hypervisor dispatches VMs on a whole core * basis. So we know that a thread sibling of the executing CPU * cannot have been preempted by the hypervisor, even if it * has called H_CONFER, which will set the yield bit. */ if (cpu_first_thread_sibling(cpu) == first_cpu) return false; /* * The specific target CPU was marked by guest OS as idle, but * then also check all other cpus in the core for PowerVM * because it does core scheduling and one of the vcpu * of the core getting preempted by hypervisor implies * other vcpus can also be considered preempted. */ first_cpu = cpu_first_thread_sibling(cpu); for (i = first_cpu; i < first_cpu + threads_per_core; i++) { if (i == cpu) continue; if (vcpu_is_dispatched(i)) return false; if (!is_vcpu_idle(i)) return true; } } #endif /* * None of the threads in target CPU's core are running but none of * them were preempted too. Hence assume the target CPU to be * non-preempted. */ return false; } static inline bool pv_is_native_spin_unlock(void) { return !is_shared_processor(); } #endif /* _ASM_POWERPC_PARAVIRT_H */
