Re: [PATCH v2 2/2] s390/kvm: Add tracepoint for DIAG 9c directed yield operations

[Sven Schnelle <svens@linux.ibm.com>]

Ciunas Bennett <ciunas@linux.ibm.com> writes:

> On 23/07/2026 16:28, Christian Borntraeger wrote:
>>
>
> [...]
>
>>> +TRACE_EVENT(kvm_s390_diag_9c,
>>> +        TP_PROTO(VCPU_PROTO_COMMON, int target_vcpu, int target_cpu,
>>> +             const char *result),
>>> +        TP_ARGS(VCPU_ARGS_COMMON, target_vcpu, target_cpu, result),
>>> +
>>> +        TP_STRUCT__entry(
>>> +            VCPU_FIELD_COMMON
>>> +            __field(int, target_vcpu)
>>> +            __field(int, target_cpu)
>>> +            __field(int, current_cpu)
>>> +            __string(result, result)
>>> +            ),
>>> +
>>> +        TP_fast_assign(
>>> +            VCPU_ASSIGN_COMMON
>>> +            __entry->target_vcpu = target_vcpu;
>>> +            __entry->target_cpu = target_cpu;
>>> +            __entry->current_cpu = smp_processor_id();
>>> +            __assign_str(result);
>>> +            ),
>>> +
>>> +        VCPU_TP_PRINTK(
>>> +               "diag=9c vcpu=%d pcpu=%d target_vcpu=%d target_pcpu=%d result=%s",
>>> +               __entry->id,
>> I think vcpu=%d re-prints __entry->id, which VCPU_TP_PRINTK()
>> already emits as the line prefix; likewise current_cpu/pcpu=%d
>> duplicates ftrace's built-in per-event CPU column.
>> Can you double check?
>
> Yes it is and I was aware that VCPU_TP_PRINTK already includes the vCPU ID
> in the prefix, but I kept it in the message for readability.
> Having all the relevant fields together in a single format string makes
> the output a bit easier to grep and follow visually I find.
> That said, if you'd prefer to keep it consistent with the other
> tracepoints, I'm happy to drop the duplicate vCPU field.

Please drop it - it should be consistent with other tracepoint, and
would only consume additional space in the trace buffer.