Re: [PATCH v6 3/4] arm64: mm: support ARCH_MMAP_RND_BITS.

From: Daniel Cashman
Date: Mon Dec 14 2015 - 15:45:29 EST


On 12/14/2015 03:19 AM, Will Deacon wrote:
>> +# max bits determined by the following formula:
>> +# VA_BITS - PAGE_SHIFT - 3
>
> Now that we have this comment, I think we can drop the unsupported
> combinations from the list below. That means we just end up with:
>
>> +config ARCH_MMAP_RND_BITS_MAX
>> + default 19 if ARM64_VA_BITS=36
>> + default 24 if ARM64_VA_BITS=39
>> + default 27 if ARM64_VA_BITS=42
>> + default 30 if ARM64_VA_BITS=47
>> + default 29 if ARM64_VA_BITS=48 && ARM64_64K_PAGES
>> + default 31 if ARM64_VA_BITS=48 && ARM64_16K_PAGES
>> + default 33 if ARM64_VA_BITS=48

Unless you object, I'd like to keep the last 3 as well, to mirror the
min bits, should any new configurations be added but not reflected here:
+ default 15 if ARM64_64K_PAGES
+ default 17 if ARM64_16K_PAGES
+ default 18

The first two of these three should be changed as well to 14 and 16.

Thanks,
Dan
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