On Mon, 27 Sep 2021, 10:33 Jan Beulich, <jbeulich@suse.com> wrote:

> On 24.09.2021 21:39, Stefano Stabellini wrote:
> > On Fri, 24 Sep 2021, Wei Chen wrote:
> >> On 2021/9/24 11:31, Stefano Stabellini wrote:
> >>> On Thu, 23 Sep 2021, Wei Chen wrote:
> >>>> --- a/xen/arch/arm/Kconfig
> >>>> +++ b/xen/arch/arm/Kconfig
> >>>> @@ -34,6 +34,17 @@ config ACPI
> >>>>      Advanced Configuration and Power Interface (ACPI) support for
> Xen is
> >>>>      an alternative to device tree on ARM64.
> >>>>   + config DEVICE_TREE_NUMA
> >>>> +  def_bool n
> >>>> +  select NUMA
> >>>> +
> >>>> +config ARM_NUMA
> >>>> +  bool "Arm NUMA (Non-Uniform Memory Access) Support (UNSUPPORTED)"
> if
> >>>> UNSUPPORTED
> >>>> +  select DEVICE_TREE_NUMA if HAS_DEVICE_TREE
> >>>
> >>> Should it be: depends on HAS_DEVICE_TREE ?
> >>> (And eventually depends on HAS_DEVICE_TREE || ACPI)
> >>>
> >>
> >> As the discussion in RFC [1]. We want to make ARM_NUMA as a generic
> >> option can be selected by users. And depends on has_device_tree
> >> or ACPI to select DEVICE_TREE_NUMA or ACPI_NUMA.
> >>
> >> If we add HAS_DEVICE_TREE || ACPI as dependencies for ARM_NUMA,
> >> does it become a loop dependency?
> >>
> >>
> https://lists.xenproject.org/archives/html/xen-devel/2021-08/msg00888.html
> >
> > OK, I am fine with that. I was just trying to catch the case where a
> > user selects "ARM_NUMA" but actually neither ACPI nor HAS_DEVICE_TREE
> > are selected so nothing happens. I was trying to make it clear that
> > ARM_NUMA depends on having at least one between HAS_DEVICE_TREE or ACPI
> > because otherwise it is not going to work.
> >
> > That said, I don't think this is important because HAS_DEVICE_TREE
> > cannot be unselected. So if we cannot find a way to express the
> > dependency, I think it is fine to keep the patch as is.
>
> So how about doing things the other way around: ARM_NUMA has no prompt
> and defaults to ACPI_NUMA || DT_NUMA, and DT_NUMA gains a prompt instead
> (and, for Arm at least, ACPI_NUMA as well; this might even be worthwhile
> to have on x86 down the road).
>

As I wrote before, I don't think the user should say "I want to enable NUMA
with Device-Tree or ACPI". Instead, they say whether they want to use NUMA
and let Xen decide to enable the DT/ACPI support.

In other word, the prompt should stay on ARM_NUMA.

Cheers,


> Jan
>
>