Re: [PATCHv6, RESEND 4/4] x86/boot/compressed/64: Handle 5-level paging boot if kernel is above 4G

From: Linus Torvalds
Date: Tue Jan 23 2018 - 12:31:23 EST


On Tue, Jan 23, 2018 at 9:09 AM, Kirill A. Shutemov
<kirill.shutemov@xxxxxxxxxxxxxxx> wrote:
>
> But if the bootloader put the kernel above 4G (not sure if anybody does
> this), we would lose control as soon as paging is disabled, because the
> code becomes unreachable to the CPU.

I do wonder if we need this. Why would a bootloader ever put the data
above 4G? Does this really happen? Wouldn't it be easier to just say
"bootloaders better put the kernel in the low 4G"?

Linus