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Subject: Re: [PATCHv2 6/7] x86/mm: remove bottom-up allocation style for
 x86_64
References: <1547183577-20309-1-git-send-email-kernelfans@gmail.com>
 <1547183577-20309-7-git-send-email-kernelfans@gmail.com>
From: Dave Hansen <dave.hansen@intel.com>
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Date: Mon, 14 Jan 2019 15:27:25 -0800
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To: Pingfan Liu <kernelfans@gmail.com>, linux-kernel@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>, Dave Hansen <dave.hansen@linux.intel.com>, Andy Lutomirski <luto@kernel.org>, Peter Zijlstra <peterz@infradead.org>, "Rafael J. Wysocki" <rjw@rjwysocki.net>, Len Brown <lenb@kernel.org>, Yinghai Lu <yinghai@kernel.org>, Tejun Heo <tj@kernel.org>, Chao Fan <fanc.fnst@cn.fujitsu.com>, Baoquan He <bhe@redhat.com>, Juergen Gross <jgross@suse.com>, Andrew Morton <akpm@linux-foundation.org>, Mike Rapoport <rppt@linux.vnet.ibm.com>, Vlastimil Babka <vbabka@suse.cz>, Michal Hocko <mhocko@suse.com>, x86@kernel.org, linux-acpi@vger.kernel.org, linux-mm@kvack.org

On 1/10/19 9:12 PM, Pingfan Liu wrote:
> Although kaslr-kernel can avoid to stain the movable node. [1]

Can you explain what staining is, or perhaps try to use some more
standard nomenclature?  There are exactly 0 instances of the word
"stain" in arch/x86/ or mm/.

> But the
> pgtable can still stain the movable node. That is a probability problem,
> although low, but exist. This patch tries to make it certainty by
> allocating pgtable on unmovable node, instead of following kernel end.

Anyway, can you read my suggested summary in the earlier patch and see
if it fits or if I missed anything?  This description is really hard to
read.

...> +#ifdef CONFIG_X86_32
> +
> +static unsigned long min_pfn_mapped;
> +
>  static unsigned long __init get_new_step_size(unsigned long step_size)
>  {
>  	/*
> @@ -653,6 +655,32 @@ static void __init memory_map_bottom_up(unsigned long map_start,
>  	}
>  }
>  
> +static unsigned long __init init_range_memory_mapping32(
> +	unsigned long r_start, unsigned long r_end)
> +{

Why is this returning a value which is not used?

Did you compile this?  Didn't you get a warning that you're not
returning a value from a function returning non-void?

Also, I'd much rather see something like this written:

static __init
unsigned long init_range_memory_mapping32(unsigned long r_start,
					  unsigned long r_end)

than what you have above.  But, if you get rid of the 'unsigned long',
it will look much more sane in the first place.