Re: [PATCH v2 0/2] Improve DIAG 9c observability

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Thu, 25 Jun 2026 15:16:13 +0200
Ciunas Bennett <ciunas@linux.ibm.com> wrote:

> This series enhances observability for DIAG 9c directed yield operations
> in s390 KVM by refactoring the handler and adding comprehensive tracing
> support.
> 
> The first patch refactors __diag_time_slice_end_directed() to use a
> single exit point with a result string variable. This consolidates the
> control flow and eliminates code duplication in logging statements,
> making the function more maintainable.
> 
> The second patch builds on this refactoring by adding a new tracepoint
> kvm_s390_diag_9c that captures detailed information about directed yield
> operations, including source/target VCPU IDs, physical CPU numbers, and
> operation results. This enables better analysis of VCPU scheduling
> behaviour and helps diagnose performance issues in virtualised s390
> environments.
> 
> Together, these changes provide kernel developers and system
> administrators with better tools to understand and debug VCPU scheduling
> patterns related to directed yields.
> 
> ---
> Changes in v2:
>  - Add system maintainers to review mail
> ---

whole series:

Acked-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

> 
> Ciunas Bennett (2):
>   s390/kvm: Refactor __diag_time_slice_end_directed for single exit
>     point
>   s390/kvm: Add tracepoint for DIAG 9c directed yield operations
> 
>  arch/s390/kvm/diag.c  | 19 +++++++++++--------
>  arch/s390/kvm/trace.h | 30 ++++++++++++++++++++++++++++++
>  2 files changed, 41 insertions(+), 8 deletions(-)
> 
> base-commit: 184fc1890bcc8242f00fee660d2651290f1461a2