linux-kernel - Re: [PATCH 3/5] x86: Only direct map addresses that are marked as E820

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Date:	Fri, 24 Aug 2012 17:30:21 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jacob Shin <jacob.shin@....com>
CC:	X86-ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	Yinghai Lu <yinghai@...nel.org>, Tejun Heo <tj@...nel.org>,
	Dave Young <dyoung@...hat.com>,
	Chao Wang <chaowang@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Borislav Petkov <borislav.petkov@....com>
Subject: Re: [PATCH 3/5] x86: Only direct map addresses that are marked as
 E820_RAM

On 08/24/2012 04:55 PM, Jacob Shin wrote:
> +
> +	for (i = 0; i < e820.nr_map; i++) {
> +		struct e820entry *ei = &e820.map[i];
> +		u64 start = ei->addr;
> +		u64 end = ei->addr + ei->size;
> +
> +		/* we only map E820_RAM */
> +		if (ei->type != E820_RAM)
> +			continue;
> +
> +		if (end <= ISA_END_ADDRESS)
> +			continue;
> +
> +		if (start <= ISA_END_ADDRESS)
> +			start = 0;
> +#ifdef CONFIG_X86_32
> +		/* on 32 bit, we only map up to max_low_pfn */
> +		if ((start >> PAGE_SHIFT) >= max_low_pfn)
> +			continue;
> +
> +		if ((end >> PAGE_SHIFT) > max_low_pfn)
> +			end = max_low_pfn << PAGE_SHIFT;
> +#endif
> +		/* the ISA range is always mapped regardless of holes */
> +		if (!pfn_range_is_mapped(0, ISA_END_ADDRESS << PAGE_SHIFT) &&
> +		    start != 0)
> +			init_memory_mapping(0, ISA_END_ADDRESS);
> +
> +		init_memory_mapping(start, end);
> +	}
> +

The ISA range mapping doesn't really make sense *inside* the loop, no? 
It seems you could do that before you enter the loop and then simply have:

+		if (end <= ISA_END_ADDRESS)
+			continue;
+
+		if (start <= ISA_END_ADDRESS)
+			start = ISA_END_ADDRESS;

... no?

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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