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powerpc/rtas: add tracepoints around RTAS entry

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Decompose the RTAS entry C code into tracing and non-tracing variants,
calling the just-added tracepoints in the tracing-enabled path. Skip
tracing in contexts known to be unsafe (real mode, CPU offline).

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230125-b4-powerpc-rtas-queue-v3-11-26929c8cce78@linux.ibm.com
This commit is contained in:
Nathan Lynch 2023-02-10 12:41:59 -06:00 committed by Michael Ellerman
parent 2c81ca7fba
commit 24098f580e
1 changed files with 53 additions and 6 deletions
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59
arch/powerpc/kernel/rtas.c
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@ -38,6 +38,7 @@
#include <asm/page.h>
#include <asm/rtas.h>
#include <asm/time.h>
#include <asm/trace.h>
#include <asm/udbg.h>
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;