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 <kirill.shutemov@xxxxxxxxxxxxxxx> > AuthorDate: Fri, 9 Feb 2018 17:22:28 +0300 > Committer: Ingo Molnar <mingo@xxxxxxxxxx> > 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" <kirill@xxxxxxxxxxxxx> > Tested-by: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> > Cc: Borislav Petkov <bp@xxxxxxx> > Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxxx> > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: linux-mm@xxxxxxxxx > Link: http://lkml.kernel.org/r/20180209142228.21231-5-kirill.shutemov@xxxxxxxxxxxxxxx > Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Tested-by should be attributed to Andrei. And please ingore my stand-alone fix that I've just posted. -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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