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

[Kirill A. Shutemov]

On Tue, Jan 23, 2018 at 09:31:16AM -0800, Linus Torvalds wrote:
> 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"?

I don't know much about bootloaders, but do we even have such guarantee
for in-kernel bootloader -- kexec?

-- 
 Kirill A. Shutemov