Re: [PATCH] arm64: mm: Fix NOMAP page initialization

[Russell King - ARM Linux <linux@armlinux.org.uk>]

On Fri, Dec 09, 2016 at 07:10:41PM +0100, Robert Richter wrote:
> On ThunderX systems with certain memory configurations we see the
> following BUG_ON():
> 
>  kernel BUG at mm/page_alloc.c:1848!
> 
> This happens for some configs with 64k page size enabled. The BUG_ON()
> checks if start and end page of a memmap range belongs to the same
> zone.
> 
> The BUG_ON() check fails if a memory zone contains NOMAP regions. In
> this case the node information of those pages is not initialized. This
> causes an inconsistency of the page links with wrong zone and node
> information for that pages. NOMAP pages from node 1 still point to the
> mem zone from node 0 and have the wrong nid assigned.
> 
> The reason for the mis-configuration is a change in pfn_valid() which
> reports pages marked NOMAP as invalid:
> 
>  68709f45385a arm64: only consider memblocks with NOMAP cleared for linear mapping
> 
> This causes pages marked as nomap being no longer reassigned to the
> new zone in memmap_init_zone() by calling __init_single_pfn().
> 
> Fixing this by implementing an arm64 specific early_pfn_valid(). This
> causes the whole mem range including NOMAP memory to be initialized by
> __init_single_page() and ensures consistency of page links to zone,
> node and section.
> 
> The HAVE_ARCH_PFN_VALID config option now requires an explicit
> definiton of early_pfn_valid() in the same way as pfn_valid(). This
> allows a customized implementation of early_pfn_valid() which
> redirects to memblock_is_memory() for arm64.
> 
> Signed-off-by: Robert Richter <rrichter@cavium.com>

Acked-by: Russell King <rmk+kernel@armlinux.org.uk>

Thanks.

> ---
>  arch/arm/include/asm/page.h   |  1 +
>  arch/arm64/include/asm/page.h |  2 ++
>  arch/arm64/mm/init.c          | 12 ++++++++++++
>  include/linux/mmzone.h        |  5 ++++-
>  4 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/include/asm/page.h b/arch/arm/include/asm/page.h
> index 4355f0ec44d6..79761bd55f94 100644
> --- a/arch/arm/include/asm/page.h
> +++ b/arch/arm/include/asm/page.h
> @@ -158,6 +158,7 @@ typedef struct page *pgtable_t;
>  
>  #ifdef CONFIG_HAVE_ARCH_PFN_VALID
>  extern int pfn_valid(unsigned long);
> +#define early_pfn_valid(pfn)	pfn_valid(pfn)
>  #endif
>  
>  #include <asm/memory.h>
> diff --git a/arch/arm64/include/asm/page.h b/arch/arm64/include/asm/page.h
> index 8472c6def5ef..17ceb7435ded 100644
> --- a/arch/arm64/include/asm/page.h
> +++ b/arch/arm64/include/asm/page.h
> @@ -49,6 +49,8 @@ typedef struct page *pgtable_t;
>  
>  #ifdef CONFIG_HAVE_ARCH_PFN_VALID
>  extern int pfn_valid(unsigned long);
> +extern int early_pfn_valid(unsigned long);
> +#define early_pfn_valid early_pfn_valid
>  #endif
>  
>  #include <asm/memory.h>
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 212c4d1e2f26..fbc136533472 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -145,11 +145,23 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
>  #endif /* CONFIG_NUMA */
>  
>  #ifdef CONFIG_HAVE_ARCH_PFN_VALID
> +
>  int pfn_valid(unsigned long pfn)
>  {
>  	return memblock_is_map_memory(pfn << PAGE_SHIFT);
>  }
>  EXPORT_SYMBOL(pfn_valid);
> +
> +/*
> + * We use memblock_is_memory() here to make sure all pages including
> + * NOMAP ranges are initialized with __init_single_page().
> + */
> +int early_pfn_valid(unsigned long pfn)
> +{
> +	return memblock_is_memory(pfn << PAGE_SHIFT);
> +}
> +EXPORT_SYMBOL(early_pfn_valid);
> +
>  #endif
>  
>  #ifndef CONFIG_SPARSEMEM
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 0f088f3a2fed..bedcf8a95881 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -1170,12 +1170,16 @@ static inline struct mem_section *__pfn_to_section(unsigned long pfn)
>  }
>  
>  #ifndef CONFIG_HAVE_ARCH_PFN_VALID
> +
>  static inline int pfn_valid(unsigned long pfn)
>  {
>  	if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
>  		return 0;
>  	return valid_section(__nr_to_section(pfn_to_section_nr(pfn)));
>  }
> +
> +#define early_pfn_valid(pfn)	pfn_valid(pfn)
> +
>  #endif
>  
>  static inline int pfn_present(unsigned long pfn)
> @@ -1200,7 +1204,6 @@ static inline int pfn_present(unsigned long pfn)
>  #define pfn_to_nid(pfn)		(0)
>  #endif
>  
> -#define early_pfn_valid(pfn)	pfn_valid(pfn)
>  void sparse_init(void);
>  #else
>  #define sparse_init()	do {} while (0)
> -- 
> 2.1.4
> 

-- 
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