On Mon, 15 Feb 2021 at 20:30, Pavel Tatashin [off-list ref] wrote:

quoted

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.

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