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

[Pierrick Bouvier]

On 12/3/24 00:45, Julian Ganz wrote:
> 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.

Does it mean that information returned should be dependent of type of 
event, as we previously discussed on v1?

> > + */
> > +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