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SubjectRe: [PATCH v3 1/2] x86/mm: Add an option to change the padding used for the physical memory mapping
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@jp.fujitsu.com>
>
> 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@jp.fujitsu.com>
> Reviewed-by: Baoquan He <bhe@redhat.com>
> ---
> 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
>

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