Nathan Lynch <nath...@linux.ibm.com> writes:
> "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?
On a P9 or P10 LPAR you should be able to use
tools/testing/selftests/powerpc/mce/inject-ra-err
cheers
