Commit 24098f58 authored by Nathan Lynch's avatar Nathan Lynch Committed by Michael Ellerman
Browse files

powerpc/rtas: add tracepoints around RTAS entry 



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: default avatarNathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230125-b4-powerpc-rtas-queue-v3-11-26929c8cce78@linux.ibm.com
parent 2c81ca7f

arch/powerpc/kernel/rtas.c

+53 −6
Original line number Diff line number Diff line
@@ -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)

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)

{

	unsigned long msr;

	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)

{

	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;