linux-kernel - Re: [PATCH v3 7/7] s390/sparsemem: provide memory_add_physaddr_to_nid() with CONFIG

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Message-ID: <20241030093017.6264-G-hca@linux.ibm.com>
Date: Wed, 30 Oct 2024 10:30:17 +0100
From: Heiko Carstens <hca@...ux.ibm.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-s390@...r.kernel.org, virtualization@...ts.linux.dev,
        linux-doc@...r.kernel.org, kvm@...r.kernel.org,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>, Thomas Huth <thuth@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        Eugenio Pérez <eperezma@...hat.com>,
        Eric Farman <farman@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH v3 7/7] s390/sparsemem: provide
 memory_add_physaddr_to_nid() with CONFIG_NUMA

On Fri, Oct 25, 2024 at 04:14:52PM +0200, David Hildenbrand wrote:
> virtio-mem uses memory_add_physaddr_to_nid() to determine the NID to use
> for memory it adds.
> 
> We currently fallback to the dummy implementation in mm/numa.c with
> CONFIG_NUMA, which will end up triggering an undesired pr_info_once():
> 
> 	Unknown online node for memory at 0x100000000, assuming node 0
> 
> On s390, we map all cpus and memory to node 0, so let's add a simple
> memory_add_physaddr_to_nid() implementation that does exactly that,
> but without complaining.
> 
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  arch/s390/include/asm/sparsemem.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
...

> diff --git a/arch/s390/include/asm/sparsemem.h b/arch/s390/include/asm/sparsemem.h
> index ff628c50afac..6377b7ea8a40 100644
> --- a/arch/s390/include/asm/sparsemem.h
> +++ b/arch/s390/include/asm/sparsemem.h
> @@ -5,4 +5,12 @@
>  #define SECTION_SIZE_BITS	27
>  #define MAX_PHYSMEM_BITS	CONFIG_MAX_PHYSMEM_BITS
>  
> +#ifdef CONFIG_NUMA
> +static inline int memory_add_physaddr_to_nid(u64 addr)
> +{
> +	return 0;
> +}
> +#define memory_add_physaddr_to_nid memory_add_physaddr_to_nid
> +#endif /* CONFIG_NUMA */
> +

We would need to have the same for phys_to_target_node(), even though
it looks like this won't be used on s390 currently.

Anyway, I'll add that, if I don't forget about it :)

For this patch:
Reviewed-by: Heiko Carstens <hca@...ux.ibm.com>