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

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Date:   Mon, 13 Nov 2017 19:02:43 +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 11/13/17 at 05:50pm, Chao Fan wrote:
> On Mon, Nov 13, 2017 at 05:26:24PM +0800, Baoquan He wrote:
  
> >> >> +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.
> >
> >No, I meant if movable_node is specified, we have to ignore
> >'kernelcore=', then we may need skip the kernel mirror handling. Since
> >kernel mirror is enabled by 'kernelcore=mirror'.
> >
> 
> Yes, the two parameters are conflict.
> Then if "movable_node" specified, we shoul not consider mirror region.
> I think there can be one another patch to handle this, but not in this
> serials. I will add the change.

Well, no.

You didn't get what I said. In process_efi_entries() mirrorred
regions are picked. If movable_node specified, mirror feature will be
ignored. That has been handled in find_zone_movable_pfns_for_nodes()
very well. So you need make it be consistent. 

And if you add a new kernel para, like immovable_mem=xx@xx, movable_node
will be expected. Anyway, please read find_zone_movable_pfns_for_nodes()
carefully.

Thanks
Baoquan
> 
> >
> >> 
> >> >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
> >> >> 
> >> >> 
> >> >> 
> >> >
> >> >
> >> 
> >> 
> >
> >
> 
>