Re: [PATCH] x86/kexec: Make kexec work in 5-level paging mode

[Matthew Wilcox]

On Mon, Jan 29, 2018 at 02:08:45PM +0300, Kirill A. Shutemov wrote:
> I've missed that we need to change relocate_kernel() to set CR4.LA57
> flag if the kernel has 5-level paging enabled.
> 
> I avoided to use ifdef CONFIG_X86_5LEVEL here and inferred if we need to
> enabled 5-level paging from previous CR4 value. This way the code is
> ready for boot-time switching between paging modes.

Forgive me if I'm missing something ... can you kexec a 5-level kernel
from a 4-level kernel or vice versa?