Re: [PATCH v4 04/23] contrib/plugins: add plugin showcasing new dicontinuity related API

[Pierrick Bouvier <pierrick.bouvier@linaro.org>]

On 5/11/25 6:13 AM, Julian Ganz wrote:
> We recently introduced new plugin API for registration of discontinuity
> related callbacks. This change introduces a minimal plugin showcasing
> the new API. It simply counts the occurances of interrupts, exceptions
> and host calls per CPU and reports the counts when exitting.
> 
> Signed-off-by: Julian Ganz <neither@nut.email>
> ---
>   contrib/plugins/meson.build |   3 +-
>   contrib/plugins/traps.c     | 100 ++++++++++++++++++++++++++++++++++++
>   docs/about/emulation.rst    |   8 +++
>   3 files changed, 110 insertions(+), 1 deletion(-)
>   create mode 100644 contrib/plugins/traps.c
> 
> +typedef struct {
> +    uint64_t interrupts;
> +    uint64_t exceptions;
> +    uint64_t hostcalls;
> +    bool active;

The scoreboard is automatically resized only when a new vcpu is 
initialized, so if an entry is present, it means it's present by definition.
Thus, you can remove the active field.

> +} TrapCounters;
> +
> +static struct qemu_plugin_scoreboard *traps;
> +static size_t max_vcpus;
> +

You can use qemu_plugin_num_vcpus() instead of keeping a copy of 
max_vcpus. It returns the number of vcpus started, which guarantees 
you'll find associated entries in any scoreboard.

[...]

With those small changes,
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>