Re: [PATCH v4 2/2] KVM: s390: add tracepoint in gmap notifier

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

On Mon,  9 Oct 2023 11:32:53 +0200
Nico Boehr <nrb@linux.ibm.com> wrote:

> The gmap notifier is called for changes in table entries with the
> notifier bit set. To diagnose performance issues, it can be useful to
> see what causes certain changes in the gmap.
> 
> Hence, add a tracepoint in the gmap notifier.
> 
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
> Acked-by: David Hildenbrand <david@redhat.com>

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

> ---
>  arch/s390/kvm/kvm-s390.c   |  2 ++
>  arch/s390/kvm/trace-s390.h | 23 +++++++++++++++++++++++
>  2 files changed, 25 insertions(+)
> 
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index b42493110d76..11676b81e6bf 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -4060,6 +4060,8 @@ static void kvm_gmap_notifier(struct gmap *gmap, unsigned long start,
>  	unsigned long prefix;
>  	unsigned long i;
>  
> +	trace_kvm_s390_gmap_notifier(start, end, gmap_is_shadow(gmap));
> +
>  	if (gmap_is_shadow(gmap))
>  		return;
>  	if (start >= 1UL << 31)
> diff --git a/arch/s390/kvm/trace-s390.h b/arch/s390/kvm/trace-s390.h
> index 6f0209d45164..9ac92dbf680d 100644
> --- a/arch/s390/kvm/trace-s390.h
> +++ b/arch/s390/kvm/trace-s390.h
> @@ -333,6 +333,29 @@ TRACE_EVENT(kvm_s390_airq_suppressed,
>  		      __entry->id, __entry->isc)
>  	);
>  
> +/*
> + * Trace point for gmap notifier calls.
> + */
> +TRACE_EVENT(kvm_s390_gmap_notifier,
> +	    TP_PROTO(unsigned long start, unsigned long end, unsigned int shadow),
> +	    TP_ARGS(start, end, shadow),
> +
> +	    TP_STRUCT__entry(
> +		    __field(unsigned long, start)
> +		    __field(unsigned long, end)
> +		    __field(unsigned int, shadow)
> +		    ),
> +
> +	    TP_fast_assign(
> +		    __entry->start = start;
> +		    __entry->end = end;
> +		    __entry->shadow = shadow;
> +		    ),
> +
> +	    TP_printk("gmap notified (start:0x%lx end:0x%lx shadow:%d)",
> +		      __entry->start, __entry->end, __entry->shadow)
> +	);
> +
>  
>  #endif /* _TRACE_KVMS390_H */
>