diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c index d2622b997b68..a6d0c46b4512 100644 --- a/arch/powerpc/kernel/rtas.c +++ b/arch/powerpc/kernel/rtas.c @@ -38,6 +38,7 @@ #include #include #include +#include #include struct rtas_filter { @@ -523,24 +524,70 @@ static const struct rtas_function *rtas_token_to_function(s32 token) /* This is here deliberately so it's only used in this file */ void enter_rtas(unsigned long); +static void __do_enter_rtas(struct rtas_args *args) +{ + enter_rtas(__pa(args)); + srr_regs_clobbered(); /* rtas uses SRRs, invalidate */ +} + +static void __do_enter_rtas_trace(struct rtas_args *args) +{ + const char *name = NULL; + /* + * If the tracepoints that consume the function name aren't + * active, avoid the lookup. + */ + if ((trace_rtas_input_enabled() || trace_rtas_output_enabled())) { + const s32 token = be32_to_cpu(args->token); + const struct rtas_function *func = rtas_token_to_function(token); + + name = func->name; + } + + trace_rtas_input(args, name); + trace_rtas_ll_entry(args); + + __do_enter_rtas(args); + + trace_rtas_ll_exit(args); + trace_rtas_output(args, name); +} + static void do_enter_rtas(struct rtas_args *args) { - unsigned long msr; - + const unsigned long msr = mfmsr(); + /* + * Situations where we want to skip any active tracepoints for + * safety reasons: + * + * 1. The last code executed on an offline CPU as it stops, + * i.e. we're about to call stop-self. The tracepoints' + * function name lookup uses xarray, which uses RCU, which + * isn't valid to call on an offline CPU. Any events + * emitted on an offline CPU will be discarded anyway. + * + * 2. In real mode, as when invoking ibm,nmi-interlock from + * the pseries MCE handler. We cannot count on trace + * buffers or the entries in rtas_token_to_function_xarray + * to be contained in the RMO. + */ + const unsigned long mask = MSR_IR | MSR_DR; + const bool can_trace = likely(cpu_online(raw_smp_processor_id()) && + (msr & mask) == mask); /* * Make sure MSR[RI] is currently enabled as it will be forced later * in enter_rtas. */ - msr = mfmsr(); BUG_ON(!(msr & MSR_RI)); BUG_ON(!irqs_disabled()); hard_irq_disable(); /* Ensure MSR[EE] is disabled on PPC64 */ - enter_rtas(__pa(args)); - - srr_regs_clobbered(); /* rtas uses SRRs, invalidate */ + if (can_trace) + __do_enter_rtas_trace(args); + else + __do_enter_rtas(args); } struct rtas_t rtas;