Re: [PATCH v2] xen: move vcpu_kick() declaration to common header

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

On 12/1/25 9:40 AM, Jan Beulich wrote:
> On 28.11.2025 17:23, Oleksii Kurochko wrote:
> > The vcpu_kick() declaration is duplicated across multiple
> > architecture-specific event.h headers (ARM, x86, PPC).
> >
> > Remove the redundant declarations and move vcpu_kick() into
> > the common xen/include/xen/sched.h header.
> >
> > Drop the definition of vcpu_kick() from ppc/include/asm/event.h,
> > as it is already provided in ppc/stubs.c.
> >
> > Add inclusion of xen/sched.h in the files where vcpu_kick() is
> > used.
> >
> > Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
Thanks.


> albeit preferably with at least ...
>
> > --- a/xen/arch/x86/cpu/mcheck/vmce.c
> > +++ b/xen/arch/x86/cpu/mcheck/vmce.c
> > @@ -12,6 +12,7 @@
> >   #include <xen/event.h>
> >   #include <xen/kernel.h>
> >   #include <xen/delay.h>
> > +#include <xen/sched.h>
> >   #include <xen/smp.h>
> >   #include <xen/mm.h>
> >   #include <asm/hvm/save.h>
> ... this change omitted. This file includes the private "mce.h", which in turn
> includes xen/sched.h.
>
> > --- a/xen/arch/x86/pv/traps.c
> > +++ b/xen/arch/x86/pv/traps.c
> > @@ -10,6 +10,7 @@
> >   #include <xen/event.h>
> >   #include <xen/hypercall.h>
> >   #include <xen/lib.h>
> > +#include <xen/sched.h>
> >   #include <xen/softirq.h>
> Somewhat similarly here, xen/event.h includes xen/sched.h. That's less obviously
> guaranteed, though, so making the include explicit here is likely okay.
I am generally okay with not adding what is probably an unnecessary new header
inclusion, but it is unclear to me why we should avoid including a header just
because it is already included by another one. In other words, if one day 
someone
removes "xen/sched.h" from "mce.h", is it acceptable for this to result in a
compilation error? How do we decide when such an error is acceptable and when
it is not?

Should the default behavior be that if header X is already included indirectly
through other headers, there is no need to include header X directly?

~ Oleksii