[PATCH 2/3] Documentation: riscv: Add documentation that describes the VM layout

[Alex Ghiti]

Le 2/25/21 à 5:34 AM, David Hildenbrand a écrit :
>                   |            |                  |         |> + 
> ffffffc000000000 | -256    GB | ffffffc7ffffffff |   32 GB | kasan
>> +   ffffffcefee00000 | -196    GB | ffffffcefeffffff |    2 MB | fixmap
>> +   ffffffceff000000 | -196    GB | ffffffceffffffff |   16 MB | PCI io
>> +   ffffffcf00000000 | -196    GB | ffffffcfffffffff |    4 GB | vmemmap
>> +   ffffffd000000000 | -192    GB | ffffffdfffffffff |   64 GB | 
>> vmalloc/ioremap space
>> +   ffffffe000000000 | -128    GB | ffffffff7fffffff |  126 GB | 
>> direct mapping of all physical memory
> 
> ^ So you could never ever have more than 126 GB, correct?
> 
> I assume that's nothing new.
> 

Before this patch, the limit was 128GB, so in my sense, there is nothing 
new. If ever we want to increase that limit, we'll just have to lower 
PAGE_OFFSET, there is still some unused virtual addresses after kasan 
for example.

Thanks,

Alex