Re: [PATCH] x86/mm: Tear down the direct map when memory hot add fails

[David Hildenbrand (Arm)]

On 11/8/26 04:00, Chris Down wrote:
> arch_add_memory() sets up the direct map before calling add_pages().
> If add_pages() fails, the range stays mapped and any page tables
> allocated for it are leaked. A later hot add can reuse the stale
> mapping.
> 
> Remove the direct mapping on failure.
> 
> Fixes: 45e0b78b0532 ("[PATCH] hot-add-mem x86_64: use CONFIG_MEMORY_HOTPLUG_RESERVE")
> Signed-off-by: Chris Down <chris@xxxxxxxxxxxxxx>
> ---
>  arch/x86/mm/init_64.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index 8b6d86fb5a42..846cb34b38dd 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -989,15 +989,23 @@ int add_pages(int nid, unsigned long start_pfn, unsigned long nr_pages,
>  	return ret;
>  }
>  
> +static void __meminit kernel_physical_mapping_remove(unsigned long start,
> +						     unsigned long end);
> +
>  int arch_add_memory(int nid, u64 start, u64 size,
>  		    struct mhp_params *params)
>  {
>  	unsigned long start_pfn = start >> PAGE_SHIFT;
>  	unsigned long nr_pages = size >> PAGE_SHIFT;
> +	int ret;
>  
>  	init_memory_mapping(start, start + size, params->pgprot);
>  
> -	return add_pages(nid, start_pfn, nr_pages, params);
> +	ret = add_pages(nid, start_pfn, nr_pages, params);
> +	if (ret)
> +		kernel_physical_mapping_remove(start, start + size);
> +
> +	return ret;
>  }
>  
>  static void __meminit free_pagetable(struct page *page)
> 
> base-commit: fa4ad798f6f681031775266044ba1b0cf3c670bd

I thought we fixed that already, but I remembered

https://lore.kernel.org/all/20260930160432.5564-1-lance.yang@xxxxxxxxx/

Acked-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>

-- 
Cheers,

David