Re: [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