From: Nathan Lynch <nath...@linux.ibm.com>
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 <nath...@linux.ibm.com>
---
arch/powerpc/kernel/rtas.c | 59 +++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 53 insertions(+), 6 deletions(-)
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 <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;
--
2.39.1
