On Tue, Feb 13, 2018 at 09:21:58AM -0800, tip-bot for Kirill A. Shutemov wrote: > Commit-ID: 89674e91fcf51f77dc4e87b77c6840f31b85077d > Gitweb: > https://git.kernel.org/tip/89674e91fcf51f77dc4e87b77c6840f31b85077d > Author: Kirill A. Shutemov <[email protected]> > AuthorDate: Fri, 9 Feb 2018 17:22:28 +0300 > Committer: Ingo Molnar <[email protected]> > CommitDate: Tue, 13 Feb 2018 18:16:22 +0100 > > x86/boot/compressed/64: Handle 5-level paging boot if kernel is above 4G > > This patch addresses a shortcoming in current boot process on machines > that supports 5-level paging. > > If a bootloader enables 64-bit mode with 4-level paging, we might need to > switch over to 5-level paging. The switching requires the disabling > paging. It works fine if kernel itself is loaded below 4G. > > 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. > > This patch implements a trampoline in lower memory to handle this > situation. > > We only need the memory for a very short time, until the main kernel > image sets up own page tables. > > We go through the trampoline even if we don't have to: if we're already > in 5-level paging mode or if we don't need to switch to it. This way the > trampoline gets tested on every boot. > > Debugged-by: "Kirill A. Shutemov" <[email protected]> > Tested-by: "Kirill A. Shutemov" <[email protected]> > Signed-off-by: Kirill A. Shutemov <[email protected]> > Cc: Andy Lutomirski <[email protected]> > Cc: Borislav Petkov <[email protected]> > Cc: Cyrill Gorcunov <[email protected]> > Cc: Linus Torvalds <[email protected]> > Cc: Matthew Wilcox <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: [email protected] > Link: > http://lkml.kernel.org/r/[email protected] > Signed-off-by: Ingo Molnar <[email protected]>
Tested-by should be attributed to Andrei. And please ingore my stand-alone fix that I've just posted. -- Kirill A. Shutemov
