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Re: [XEN RFC PATCH 03/40] xen/x86: Initialize memnodemapsize while faking NUMA node

  • To: Wei Chen <wei.chen@xxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Thu, 12 Aug 2021 17:32:57 +0200
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  • Cc: Bertrand.Marquis@xxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, sstabellini@xxxxxxxxxx, julien@xxxxxxx
  • Delivery-date: Thu, 12 Aug 2021 15:33:20 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 11.08.2021 12:23, Wei Chen wrote:
> When system turns NUMA off or system lacks of NUMA support,
> Xen will fake a NUMA node to make system works as a single
> node NUMA system.
> In this case the memory node map doesn't need to be allocated
> from boot pages. But we should set the memnodemapsize to the
> array size of _memnodemap. Xen hadn't done it, and Xen should
> assert in phys_to_nid. But because x86 was using an empty
> macro "VIRTUAL_BUG_ON" to replace ASSERT, this bug will not
> be triggered.

How about we promote VIRTUAL_BUG_ON() to expand to at least ASSERT()?

> --- a/xen/arch/x86/numa.c
> +++ b/xen/arch/x86/numa.c
> @@ -270,6 +270,8 @@ void __init numa_initmem_init(unsigned long start_pfn, 
> unsigned long end_pfn)
>      /* setup dummy node covering all memory */
>      memnode_shift = BITS_PER_LONG - 1;
>      memnodemap = _memnodemap;
> +    memnodemapsize = ARRAY_SIZE(_memnodemap);

But this doesn't reflect reality then, does it? We'd rather want to
set the size to 1, I would think.




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