Re: [PATCH v2 1/1] arm64: mm: correct the inside linear map boundaries during hotplug check

[Ard Biesheuvel]

On Mon, 15 Feb 2021 at 20:30, Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> wrote:
>
> > Can't we simply use signed arithmetic here? This expression works fine
> > if the quantities are all interpreted as s64 instead of u64
>
> I was thinking about that, but I do not like the idea of using sign
> arithmetics for physical addresses. Also, I am worried that someone in
> the future will unknowingly change it to unsigns or to phys_addr_t. It
> is safer to have start explicitly set to 0 in case of wrap.

memstart_addr is already a s64 for this exact reason.

Btw, the KASLR check is incorrect: memstart_addr could also be
negative when running the 52-bit VA kernel on hardware that is only
48-bit VA capable.