On Tue, Jan 23, 2018 at 08:37:03PM +0300, Kirill A. Shutemov wrote: > 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 > > <[email protected]> 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?
There's no such guarantee, so we need it at least for kexec. -Andi
