Re: [RFC PATCH v3 01/11] plugins: add types for callbacks related to certain discontinuities

["Julian Ganz" <neither@nut.email>]

Hi,

December 2, 2024 at 8:26 PM, "Julian Ganz" wrote:
> diff --git a/include/qemu/qemu-plugin.h b/include/qemu/qemu-plugin.h
> index 0fba36ae02..9c67374b7e 100644
> --- a/include/qemu/qemu-plugin.h
> +++ b/include/qemu/qemu-plugin.h
> @@ -154,6 +154,49 @@ typedef void (*qemu_plugin_vcpu_simple_cb_t)(qemu_plugin_id_t id,
<snip>
> +/**
> + * typedef qemu_plugin_vcpu_discon_cb_t - vcpu discontinuity callback
> + * @vcpu_index: the current vcpu context
> + * @type: the type of discontinuity
> + * @from_pc: the source of the discontinuity, e.g. the PC before the
> + * transition
> + * @to_pc: the PC pointing to the next instruction to be executed
> + *
> + * The excact semantics of @from_pc depends on @the type of discontinuity. For
> + * interrupts, @from_pc will point to the next instruction which would have
> + * been executed. For exceptions and host calls, @from_pc will point to the
> + * instruction that caused the exception or issued the host call. Note that
> + * in the case of exceptions, the instruction is not retired and thus not
> + * observable via general instruction exec callbacks. The same may be the case
> + * for some host calls such as hypervisor call "exceptions".

Some more notes about this bit: I originally tried to make the from_pc
semantics independent from the type of event, i.e. either of the two
cases. I obviously did not succeed in doing so. As, in most cases, the
instruction pointed to by from_pc is not observable via exec callbacks
I could also not test this behaviour in the testing plugin (see patch
11). I am therefore in favor for dropping the from_pc for the next
iteration of this patch series.

> + */
> +typedef void (*qemu_plugin_vcpu_discon_cb_t)(qemu_plugin_id_t id,
> + unsigned int vcpu_index,
> + enum qemu_plugin_discon_type type,
> + uint64_t from_pc, uint64_t to_pc);
> +
>  /**
>  * qemu_plugin_uninstall() - Uninstall a plugin
>  * @id: this plugin's opaque ID
> -- 
> 2.45.2
>

Regards,
Julian