Re: [PATCH v3 1/2] x86/mm: Add an option to change the padding used for the physical memory mapping

[Masayoshi Mizuma]

Ping...
I would appreciate if someone could review it because this patch
fixes the real memory hotplug issue...

On Tue, Sep 04, 2018 at 11:11:40AM -0400, Masayoshi Mizuma wrote:
> From: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx>
> 
> If each node of physical memory layout has huge space for hotplug,
> the padding used for the physical memory mapping section is not enough.
> For exapmle of the layout:
>   SRAT: Node 6 PXM 4 [mem 0x100000000000-0x13ffffffffff] hotplug
>   SRAT: Node 7 PXM 5 [mem 0x140000000000-0x17ffffffffff] hotplug
>   SRAT: Node 2 PXM 6 [mem 0x180000000000-0x1bffffffffff] hotplug
>   SRAT: Node 3 PXM 7 [mem 0x1c0000000000-0x1fffffffffff] hotplug
> 
> We can increase the padding by CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING,
> however, the needed padding size depends on the system environment.
> The kernel option is better than changing the config.
> 
> Change log from v2:
>  - Simplify the description. As Baoquan said, this is simillar SGI UV issue,
>    but a little different. Remove SGI UV description.
> 
> Signed-off-by: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx>
> Reviewed-by: Baoquan He <bhe@xxxxxxxxxx>
> ---
>  arch/x86/mm/kaslr.c | 17 ++++++++++++++++-
>  1 file changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
> index 61db77b0eda9..aeb62615bd46 100644
> --- a/arch/x86/mm/kaslr.c
> +++ b/arch/x86/mm/kaslr.c
> @@ -40,6 +40,7 @@
>   */
>  static const unsigned long vaddr_end = CPU_ENTRY_AREA_BASE;
>  
> +static int __initdata rand_mem_physical_padding = CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING;
>  /*
>   * Memory regions randomized by KASLR (except modules that use a separate logic
>   * earlier during boot). The list is ordered based on virtual addresses. This
> @@ -69,6 +70,20 @@ static inline bool kaslr_memory_enabled(void)
>  	return kaslr_enabled() && !IS_ENABLED(CONFIG_KASAN);
>  }
>  
> +static int __init rand_mem_physical_padding_setup(char *str)
> +{
> +	int max_padding = (1 << (MAX_PHYSMEM_BITS - TB_SHIFT)) - 1;
> +
> +	get_option(&str, &rand_mem_physical_padding);
> +	if (rand_mem_physical_padding < 0)
> +		rand_mem_physical_padding = 0;
> +	else if (rand_mem_physical_padding > max_padding)
> +		rand_mem_physical_padding = max_padding;
> +
> +	return 0;
> +}
> +early_param("rand_mem_physical_padding", rand_mem_physical_padding_setup);
> +
>  /* Initialize base and padding for each memory region randomized with KASLR */
>  void __init kernel_randomize_memory(void)
>  {
> @@ -102,7 +117,7 @@ void __init kernel_randomize_memory(void)
>  	 */
>  	BUG_ON(kaslr_regions[0].base != &page_offset_base);
>  	memory_tb = DIV_ROUND_UP(max_pfn << PAGE_SHIFT, 1UL << TB_SHIFT) +
> -		CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING;
> +		rand_mem_physical_padding;
>  
>  	/* Adapt phyiscal memory region size based on available memory */
>  	if (memory_tb < kaslr_regions[0].size_tb)
> -- 
> 2.18.0
>