Re: [XEN PATCH v1] xen: mem_access: conditionally compile vm_event.c & monitor.c

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

On Mon, Jan 6, 2025 at 5:16 AM Jan Beulich <jbeulich@xxxxxxxx> wrote:
>
> On 30.12.2024 07:30, Sergiy Kibrik wrote:
> > From: Stefano Stabellini <stefano.stabellini@xxxxxxx>
> >
> > Extend coverage of CONFIG_MEM_ACCESS option and make the build of VM events
> > and monitoring support optional.
>
> Yet doesn't this end up in things becoming misleading? Don't we rather need a
> 2nd Kconfig option, with a dependency between the two? Or alternatively a
> rename of the existing option (to describe the higher-level feature rather
> than the lower level one)? Tamas, I'm particularly interested in knowing your
> view here as well.

Thanks Jan, I was thinking the same thing. The dependency of these
subsystems is mem_access -> monitor -> vm_event. If the goal here is
to disable all three levels the ideal way would be to have separate
kconfig options for each level. It may be a bit too fine-grained
though on ARM since there are only two types of events for monitor
(SMC & mem_access) and only the monitor uses the vm_event channel (no
mem-sharing/paging on ARM). So if doing separate kconfig for each
individual feature is an overkill I would suggest using
CONFIG_VM_EVENT that disables all three levels, including both
mem_access & smc monitor hooks.

Tamas