Subject: Re: [PATCH v4 24/26] arch_numa: switch over to numa_memblks

From: Marc Zyngier <[email-masked]>
Date: Wed, 27 Nov 2024 19:32:06 +0000

Hi Mike,

Sorry for reviving a rather old thread.

On Wed, 07 Aug 2024 07:41:08 +0100,
Mike Rapoport <[email-masked]> wrote:
> 
> From: "Mike Rapoport (Microsoft)" <[email-masked]>
> 
> Until now arch_numa was directly translating firmware NUMA information
> to memblock.
> 
> Using numa_memblks as an intermediate step has a few advantages:
> * alignment with more battle tested x86 implementation
> * availability of NUMA emulation
> * maintaining node information for not yet populated memory
> 
> Adjust a few places in numa_memblks to compile with 32-bit phys_addr_t
> and replace current functionality related to numa_add_memblk() and
> __node_distance() in arch_numa with the implementation based on
> numa_memblks and add functions required by numa_emulation.
> 
> Signed-off-by: Mike Rapoport (Microsoft) <[email-masked]>
> Tested-by: Zi Yan <[email-masked]> # for x86_64 and arm64
> Reviewed-by: Jonathan Cameron <[email-masked]>
> Tested-by: Jonathan Cameron <[email-masked]> [arm64 + CXL via QEMU]
> Acked-by: Dan Williams <[email-masked]>
> Acked-by: David Hildenbrand <[email-masked]>
> ---
>  drivers/base/Kconfig       |   1 +
>  drivers/base/arch_numa.c   | 201 +++++++++++--------------------------
>  include/asm-generic/numa.h |   6 +-
>  mm/numa_memblks.c          |  17 ++--
>  4 files changed, 75 insertions(+), 150 deletions(-)
>

[...]

>  static int __init numa_register_nodes(void)
>  {
>  	int nid;
> -	struct memblock_region *mblk;
> -
> -	/* Check that valid nid is set to memblks */
> -	for_each_mem_region(mblk) {
> -		int mblk_nid = memblock_get_region_node(mblk);
> -		phys_addr_t start = mblk->base;
> -		phys_addr_t end = mblk->base + mblk->size - 1;
> -
> -		if (mblk_nid == NUMA_NO_NODE || mblk_nid >= MAX_NUMNODES) {
> -			pr_warn("Warning: invalid memblk node %d [mem %pap-%pap]\n",
> -				mblk_nid, &start, &end);
> -			return -EINVAL;
> -		}
> -	}
>  

This hunk has the unfortunate side effect of killing my ThunderX
extremely early at boot time, as this sorry excuse for a machine
really relies on the kernel recognising that whatever NUMA information
the FW offers is BS.

Reverting this hunk restores happiness (sort of).

FWIW, I've posted a patch with such revert at [1].

Thanks,

	M.

[1] https://lore.kernel.org/r/[email-masked]

-- 
Without deviation from the norm, progress is not possible.