Re: [PATCH -next] RISCV: Add some depends for NUMA

[Palmer Dabbelt]

On Wed, 03 Feb 2021 06:23:43 PST (-0800), wangkefeng.wang@xxxxxxxxxx wrote:
> The numa feature is useless for riscv32 platform(MAXPHYSMEM_1GB if 32bit),

I'm not convinced of that.  There's no reason NUMA shouldn't work on 32-bit, it
doesn't depend on having a large amount of memory just having non-uniform
memory.  I could buy the argument that build a 32-bit NUMA system would be
wacky, but IIUC it works now and I don't see any reason to throw that away.

> and it should depends on SMP feature, this also fix the build error,

I can buy that CONFIG_NUMA doesn't really make sense without CONFIG_SMP, as
there's not a whole lot to do, but I also don't see any reason from disallowing
users from picking it.  arm64 allows !SMP && NUMA, and I don't see any reason
it wouldn't work just as well for us.

>   riscv64-buildroot-linux-gnu-ld: mm/page_alloc.o: in function `.L0 ':
>   page_alloc.c:(.text+0x4808): undefined reference to `node_reclaim_distance'

The only instance of node_reclaim_distance I see in mm/page_alloc.c is already
guarded with CONFIG_NUMA, but the definition of node_reclaim_distance isn't.
I'll send out some patches to add the guard which might make sorting this out
earlier, but I don't see it fixing any failures.

> Fixes: 4f0e8eef772e ("riscv: Add numa support for riscv64 platform")
> Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> ---
>  arch/riscv/Kconfig | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 22fa17898d29..ac7f5801bd82 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -312,6 +312,8 @@ endchoice
>  # Common NUMA Features
>  config NUMA
>  	bool "NUMA Memory Allocation and Scheduler Support"
> +	depends on SMP
> +	depends on 64BIT
>  	select GENERIC_ARCH_NUMA
>  	select OF_NUMA
>  	select ARCH_SUPPORTS_NUMA_BALANCING