linux-kernel - Re: [PATCH v2 2/4] kaslr: select the memory region in immovable node to process

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Message-ID: <20171113083131.GE10474@x1>
Date:   Mon, 13 Nov 2017 16:31:31 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Chao Fan <fanc.fnst@...fujitsu.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, hpa@...or.com,
        tglx@...utronix.de, mingo@...hat.com, keescook@...omium.org,
        yasu.isimatu@...il.com, indou.takao@...fujitsu.com,
        caoj.fnst@...fujitsu.com, douly.fnst@...fujitsu.com
Subject: Re: [PATCH v2 2/4] kaslr: select the memory region in immovable node
 to process

On 11/01/17 at 07:32pm, Chao Fan wrote:
> Compare the region of memmap entry and immovable_mem, then choose the
> intersection to process_mem_region.
> 
> Since the interrelationship between e820 or efi entries and memory
> region in immovable_mem is different:
> One memory region in one node may contain several entries of e820 or
> efi sometimes, and one entry of e820 or efi may contain the memory in
> different nodes sometimes.
> It may split one node or one entry to several regions.
> 
> Signed-off-by: Chao Fan <fanc.fnst@...fujitsu.com>
> ---
>  arch/x86/boot/compressed/kaslr.c | 60 ++++++++++++++++++++++++++++++++++------
>  1 file changed, 52 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index 0a591c0023f1..fcd640fdeaed 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -634,6 +634,54 @@ static void process_mem_region(struct mem_vector *entry,
>  	}
>  }
>  
> +static bool select_immovable_node(struct mem_vector region,
> +				  unsigned long long minimum,
> +				  unsigned long long image_size)
> +{

About this patch, I just want to notice two things:
1) From the current code, 'movable_node' kernel parameter is exclusive.
In find_zone_movable_pfns_for_nodes(), you can see that 'kernelcore' and
'movablecore' will be ignored as long as 'movable_node' is specified.
Please also consider this in your code here. If 'movable_node' has to be
specified too, and need skip the kernel mirror handling.

2)process_mem_region() is a key function to process the available memory
regions. Please don't make another process_mem_region() like below. You
can write a small helper function to find the immovable_mem[] which is
intersecting with the passed in memory region and use clamp() to get
the real available region. You 'REALLY' don't need to split the region
in your so called 'select_immovable_node()' function here.

PLEASE elaborate more on these details before post.

Thanks
Baoquan

> +	int i;
> +
> +	/* If no immovable_mem stored, use region directly */
> +	if (num_immovable_region == 0) {
> +		process_mem_region(&region, minimum, image_size);
> +
> +		if (slot_area_index == MAX_SLOT_AREA) {
> +			debug_putstr("Aborted memmap scan (slot_areas full)!\n");
> +			return 1;
> +		}
> +	} else {
> +		/*
> +		 * Walk all immovable regions, and filter the intersection
> +		 * to process_mem_region.
> +		 */
> +		for (i = 0; i < num_immovable_region; i++) {
> +			struct mem_vector entry;
> +			unsigned long long start, end, select_end, region_end;
> +
> +			region_end = region.start + region.size - 1;
> +			start = immovable_mem[i].start;
> +			end = start + immovable_mem[i].size - 1;
> +
> +			if (region_end < start || region.start > end)
> +				continue;
> +
> +			/* May split one region to several entries. */
> +			entry.start = start > region.start ?
> +				      start : region.start;
> +			select_end = end > region_end ? region_end : end;
> +
> +			entry.size = select_end - entry.start + 1;
> +
> +			process_mem_region(&entry, minimum, image_size);
> +
> +			if (slot_area_index == MAX_SLOT_AREA) {
> +				debug_putstr("Aborted memmap scan (slot_areas full)!\n");
> +				return 1;
> +			}
> +		}
> +	}
> +	return 0;
> +}
> +
>  #ifdef CONFIG_EFI
>  /*
>   * Returns true if mirror region found (and must have been processed
> @@ -699,11 +747,9 @@ process_efi_entries(unsigned long minimum, unsigned long image_size)
>  
>  		region.start = md->phys_addr;
>  		region.size = md->num_pages << EFI_PAGE_SHIFT;
> -		process_mem_region(&region, minimum, image_size);
> -		if (slot_area_index == MAX_SLOT_AREA) {
> -			debug_putstr("Aborted EFI scan (slot_areas full)!\n");
> +
> +		if (select_immovable_node(region, minimum, image_size))
>  			break;
> -		}
>  	}
>  	return true;
>  }
> @@ -730,11 +776,9 @@ static void process_e820_entries(unsigned long minimum,
>  			continue;
>  		region.start = entry->addr;
>  		region.size = entry->size;
> -		process_mem_region(&region, minimum, image_size);
> -		if (slot_area_index == MAX_SLOT_AREA) {
> -			debug_putstr("Aborted e820 scan (slot_areas full)!\n");
> +
> +		if (select_immovable_node(region, minimum, image_size))
>  			break;
> -		}
>  	}
>  }
>  
> -- 
> 2.13.6
> 
> 
>