Re: [PATCH v2 RESEND 13/18] x86, numa, mem_hotplug: Skip all the regions the kernel resides in.

[Tang Chen <tangchen@cn.fujitsu.com>]

Hi tj,

I have resent the v2 patch-set. Would you please give some more
comments about the memblock and x86 booting code modification ?

And I'm also discussing with the ACPICA guys about the implementation
on ACPI side. I hope we can catch up with 3.12 this time.

Thanks.

On 08/02/2013 05:14 PM, Tang Chen wrote:
> At early time, memblock will reserve some memory for the kernel,
> such as the kernel code and data segments, initrd file, and so on，
> which means the kernel resides in these memory regions.
>
> Even if these memory regions are hotpluggable, we should not
> mark them as hotpluggable. Otherwise the kernel won't have enough
> memory to boot.
>
> This patch finds out which memory regions the kernel resides in,
> and skip them when finding all hotpluggable memory regions.
>
> Signed-off-by: Tang Chen<tangchen@cn.fujitsu.com>
> Reviewed-by: Zhang Yanfei<zhangyanfei@cn.fujitsu.com>
> ---
>   mm/memory_hotplug.c |   45 +++++++++++++++++++++++++++++++++++++++++++++
>   1 files changed, 45 insertions(+), 0 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index ef9ccf8..10a30ef 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -31,6 +31,7 @@
>   #include<linux/firmware-map.h>
>   #include<linux/stop_machine.h>
>   #include<linux/acpi.h>
> +#include<linux/memblock.h>
>
>   #include<asm/tlbflush.h>
>
> @@ -93,6 +94,40 @@ static void release_memory_resource(struct resource *res)
>
>   #ifdef CONFIG_ACPI_NUMA
>   /**
> + * kernel_resides_in_range - Check if kernel resides in a memory region.
> + * @base: The base address of the memory region.
> + * @length: The length of the memory region.
> + *
> + * This function is used at early time. It iterates memblock.reserved and check
> + * if the kernel has used any memory in [@base, @base + @length).
> + *
> + * Return true if the kernel resides in the memory region, false otherwise.
> + */
> +static bool __init kernel_resides_in_region(phys_addr_t base, u64 length)
> +{
> +	int i;
> +	phys_addr_t start, end;
> +	struct memblock_region *region;
> +	struct memblock_type *reserved =&memblock.reserved;
> +
> +	for (i = 0; i<  reserved->cnt; i++) {
> +		region =&reserved->regions[i];
> +
> +		if (region->flags != MEMBLOCK_HOTPLUG)
> +			continue;
> +
> +		start = region->base;
> +		end = region->base + region->size;
> +		if (end<= base || start>= base + length)
> +			continue;
> +
> +		return true;
> +	}
> +
> +	return false;
> +}
> +
> +/**
>    * find_hotpluggable_memory - Find out hotpluggable memory from ACPI SRAT.
>    *
>    * This function did the following:
> @@ -129,6 +164,16 @@ void __init find_hotpluggable_memory(void)
>
>   	while (ACPI_SUCCESS(acpi_hotplug_mem_affinity(srat_vaddr,&base,
>   						&size,&offset))) {
> +		/*
> +		 * At early time, memblock will reserve some memory for the
> +		 * kernel, such as the kernel code and data segments, initrd
> +		 * file, and so on，which means the kernel resides in these
> +		 * memory regions. These regions should not be hotpluggable.
> +		 * So do not mark them as hotpluggable.
> +		 */
> +		if (kernel_resides_in_region(base, size))
> +			continue;
> +
>   		/* Will mark hotpluggable memory regions here */
>   	}
>

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