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

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Message-ID: <20171113091840.GF15416@localhost.localdomain>
Date:   Mon, 13 Nov 2017 17:18:41 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.com>
To:     Baoquan He <bhe@...hat.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 Mon, Nov 13, 2017 at 04:31:31PM +0800, Baoquan He wrote:
>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.
>

Thanks for the notice, I will add the similar operation.

>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.
>

OK, I will try to make a new method, which is smaller and better to
filter the regions.

Thanks,
Chao Fan

>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
>> 
>> 
>> 
>
>