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@xxxxxxxxxx>
Acked-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
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
>
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>