Re: 4.14.9 with CONFIG_MCORE2 fails to boot

[Greg KH <greg@kroah.com>]

On Thu, Dec 28, 2017 at 12:33:22PM +0300, Alexander Tsoy wrote:
> Hello,
> 
> 4.14.9 fails to boot if CONFIG_MCORE2 is enabled and when compiled with
> gcc 6+. More details in the following bug reports:
> https://bugzilla.kernel.org/show_bug.cgi?id=198263
> https://bugs.gentoo.org/642268
> 
> I bisected it to the commit below:
> 
> $ git bisect good
> 2bc9fa0beaf10206a778f02e9e5cb62f50345b1a is the first bad commit
> commit 2bc9fa0beaf10206a778f02e9e5cb62f50345b1a
> Author: Andy Lutomirski <luto@kernel.org>
> Date:   Mon Dec 4 15:07:23 2017 +0100
> 
>     x86/entry/64: Use a per-CPU trampoline stack for IDT entries
> 
>     commit 7f2590a110b837af5679d08fc25c6227c5a8c497 upstream.
> 
>     Historically, IDT entries from usermode have always gone directly
>     to the running task's kernel stack.  Rearrange it so that we enter
> on
>     a per-CPU trampoline stack and then manually switch to the task's
> stack.
>     This touches a couple of extra cachelines, but it gives us a chance
>     to run some code before we touch the kernel stack.
> 
>     The asm isn't exactly beautiful, but I think that fully refactoring
>     it can wait.
> 
>     Signed-off-by: Andy Lutomirski <luto@kernel.org>
>     Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>     Reviewed-by: Borislav Petkov <bp@suse.de>
>     Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
>     Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
>     Cc: Borislav Petkov <bp@alien8.de>
>     Cc: Borislav Petkov <bpetkov@suse.de>
>     Cc: Brian Gerst <brgerst@gmail.com>
>     Cc: Dave Hansen <dave.hansen@intel.com>
>     Cc: Dave Hansen <dave.hansen@linux.intel.com>
>     Cc: David Laight <David.Laight@aculab.com>
>     Cc: Denys Vlasenko <dvlasenk@redhat.com>
>     Cc: Eduardo Valentin <eduval@amazon.com>
>     Cc: Greg KH <gregkh@linuxfoundation.org>
>     Cc: H. Peter Anvin <hpa@zytor.com>
>     Cc: Josh Poimboeuf <jpoimboe@redhat.com>
>     Cc: Juergen Gross <jgross@suse.com>
>     Cc: Linus Torvalds <torvalds@linux-foundation.org>
>     Cc: Peter Zijlstra <peterz@infradead.org>
>     Cc: Rik van Riel <riel@redhat.com>
>     Cc: Will Deacon <will.deacon@arm.com>
>     Cc: aliguori@amazon.com
>     Cc: daniel.gruss@iaik.tugraz.at
>     Cc: hughd@google.com
>     Cc: keescook@google.com
>     Link: https://lkml.kernel.org/r/20171204150606.225330557@linutronix
> .de
>     Signed-off-by: Ingo Molnar <mingo@kernel.org>
>     Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 
> :040000 040000 275d4746936a9e521a2b5041856f7dc1d1820dc6
> 8f8e869fd59c3dd781dceffa76e53e41d733a0cf M      arch
> 
> $ git bisect log
> git bisect start
> # bad: [dad5c1402c570cd07a80113784bc20a7f930c8ae] Linux 4.14.9
> git bisect bad dad5c1402c570cd07a80113784bc20a7f930c8ae
> # good: [7b3775017f4e6b87dfd2c7f63d1eaf057948f31d] Linux 4.14.8
> git bisect good 7b3775017f4e6b87dfd2c7f63d1eaf057948f31d
> # good: [d120cd749ef9770ee98b708a83b49547dcf1c0e1] x86/entry/64:
> Separate cpu_current_top_of_stack from TSS.sp0
> git bisect good d120cd749ef9770ee98b708a83b49547dcf1c0e1
> # bad: [97f41b41c432e5a80c91445d92c2f4b729984d36] powerpc/xmon: Avoid
> tripping SMP hardlockup watchdog
> git bisect bad 97f41b41c432e5a80c91445d92c2f4b729984d36
> # bad: [bfd66a406fe7e590055c1d6714adc697f18664c8] PCI: Avoid bus reset
> if bridge itself is broken
> git bisect bad bfd66a406fe7e590055c1d6714adc697f18664c8
> # bad: [8388d287e361a2fd0a39bece30a736d692d5c3d8] x86/cpufeatures: Make
> CPU bugs sticky
> git bisect bad 8388d287e361a2fd0a39bece30a736d692d5c3d8
> # bad: [bb568391775d4a840992e2d2493f39d6e86401e3] x86/entry/64: Move
> the IST stacks into struct cpu_entry_area
> git bisect bad bb568391775d4a840992e2d2493f39d6e86401e3
> # bad: [2bc9fa0beaf10206a778f02e9e5cb62f50345b1a] x86/entry/64: Use a
> per-CPU trampoline stack for IDT entries
> git bisect bad 2bc9fa0beaf10206a778f02e9e5cb62f50345b1a
> # good: [c3dbef1bd0f7eb09daf49409ea533aa1b0eeb82e] x86/espfix/64: Stop
> assuming that pt_regs is on the entry stack
> git bisect good c3dbef1bd0f7eb09daf49409ea533aa1b0eeb82e
> # first bad commit: [2bc9fa0beaf10206a778f02e9e5cb62f50345b1a]
> x86/entry/64: Use a per-CPU trampoline stack for IDT entries

Thanks for letting us know.  Does Linus's current tree also have this
same problem for you?

greg k-h