Hi Stefano, > -----Original Message----- > From: Stefano Stabellini <sstabell...@kernel.org> > Sent: 2021年9月28日 1:17 > To: Jan Beulich <jbeul...@suse.com> > Cc: Julien Grall <julien.grall....@gmail.com>; Stefano Stabellini > <sstabell...@kernel.org>; Wei Chen <wei.c...@arm.com>; xen-devel <xen- > de...@lists.xenproject.org>; Bertrand Marquis <bertrand.marq...@arm.com> > Subject: Re: [PATCH 36/37] xen/arm: Provide Kconfig options for Arm to > enable NUMA > > On Mon, 27 Sep 2021, Jan Beulich wrote: > > On 27.09.2021 10:45, Julien Grall wrote: > > > On Mon, 27 Sep 2021, 10:33 Jan Beulich, <jbeul...@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. > > > > Okay. In which case I'm confused by Stefano's question. > > Let me clarify: I think it is fine to have a single prompt for NUMA in > Kconfig. However, I am just pointing out that it is theoretically > possible with the current code to present an ARM_NUMA prompt to the user > but actually have no NUMA enabled at the end because both DEVICE TREE > and ACPI are disabled. This is only a theoretical problem because DEVICE > TREE support (HAS_DEVICE_TREE) cannot be disabled today. Also I cannot > imagine how a configuration with neither DEVICE TREE nor ACPI can be > correct. So I don't think it is a critical concern. > > That said, you can see that, at least theoretically, ARM_NUMA depends on > either HAS_DEVICE_TREE or ACPI, so I suggested to add: > > depends on HAS_DEVICE_TREE || ACPI > > Wei answered that it might introduce a circular dependency, but I did > try the addition of "depends on HAS_DEVICE_TREE || ACPI" under ARM_NUMA > in Kconfig and everything built fine here.
Ok, I will add "depends on HAS_DEVICE_TREE" in next version, but "|| ACPI" will be later when we have ACPI NUMA for Arm : )
