Messages in this thread |  | | From | Eric Dumazet <> | Subject | instant reboot caused by 194a9749c73d650c0 | Date | Sat, 14 Apr 2018 21:39:26 -0700 |
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Hi Kirill
For some reason, my hosts instantly crash at boot time, with absolutely no log on console.
Bisection pointed to :
$ git bisect bad 194a9749c73d650c0b1dfdee04fb0bdf0a888ba8 is the first bad commit commit 194a9749c73d650c0b1dfdee04fb0bdf0a888ba8 Author: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Date: Mon Mar 12 13:02:46 2018 +0300
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.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Borislav Petkov <bp@suse.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/20180312100246.89175-5-kirill.shutemov@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reverting this patch solves the problem for me.
Thanks.
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