On Tue Nov 29, 2022 at 9:44 AM AEST, Nathan Lynch wrote: > "Nicholas Piggin" <npig...@gmail.com> writes: > > > On Sat Nov 19, 2022 at 1:07 AM AEST, Nathan Lynch wrote: > >> Call the just-added rtas tracepoints in do_enter_rtas(), taking care > >> to avoid function name lookups in the CPU offline path. > >> > >> Signed-off-by: Nathan Lynch <nath...@linux.ibm.com> > >> --- > >> arch/powerpc/kernel/rtas.c | 23 +++++++++++++++++++++++ > >> 1 file changed, 23 insertions(+) > >> > >> diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c > >> index 198366d641d0..3487b42cfbf7 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> > >> > >> enum rtas_function_flags { > >> @@ -525,6 +526,7 @@ void enter_rtas(unsigned long); > >> static void do_enter_rtas(struct rtas_args *args) > >> { > >> unsigned long msr; > >> + const char *name = NULL; > >> > >> /* > >> * Make sure MSR[RI] is currently enabled as it will be forced later > >> @@ -537,9 +539,30 @@ static void do_enter_rtas(struct rtas_args *args) > >> > >> hard_irq_disable(); /* Ensure MSR[EE] is disabled on PPC64 */ > >> > >> + if ((trace_rtas_input_enabled() || trace_rtas_output_enabled())) { > >> + /* > >> + * rtas_token_to_function() uses xarray which uses RCU, > >> + * but this code can run in the CPU offline path > >> + * (e.g. stop-self), after it's become invalid to call > >> + * RCU APIs. > >> + */ > > > > We can call this in real-mode via pseries_machine_check_realmode > > -> fwnmi_release_errinfo, so tracing should be disabled for that > > case too... Does this_cpu_set_ftrace_enabled(0) in the early > > machine check handler cover that sufficiently? > > I suspect so, but I'd like to verify. Do you know how I could exercise > this path in qemu or LPAR?
I have some machine check injection patches for qemu but they never got merged... I can point you to them if you need. Should try get those merged again. Thanks, Nick