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Date:   Fri, 27 Jul 2018 15:25:42 +0200
From:   Joerg Roedel <jroedel@suse.de>
To:     kernel test robot <lkp@intel.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        linux-security-module@vger.kernel.org,
        linux-kernel@vger.kernel.org, LKP <lkp@01.org>
Subject: Re: [lkp-robot] [confidence: ] 7757d607c6 [   56.996267] BUG: Bad
 page map in process trinity-c2  pte:0d755065 pmd:0d55b067
Message-ID: <20180727132542.mt35m3knpwpsyb73@suse.de>
References: <20180721022325.GF12513@shao2-debian>
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Hey,

thanks for the report! It did a lot of testing and the issue is fixed
now with this patch:

	https://lore.kernel.org/lkml/1532533683-5988-4-git-send-email-joro@8bytes.org/

I did 2150 runs of your reproducer with the reproducer attached to this
report, and the issue triggered three times.

With the patch above the issue did not trigger anymore in (up to now)
2170 runs of the reproducer.

On Sat, Jul 21, 2018 at 10:23:25AM +0800, kernel test robot wrote:
> git bisect start 8c934e01a7ce685d98e970880f5941d79272c654 37b5dca2898d1471729194f45e281c2443eb9d6c --
> git bisect good 8372d66865deb45ee3ec21401a9c80f231b728c8  # 23:36  G    304     0    4   4  x86/pgtable: Move pgdp kernel/user conversion functions to pgtable.h
> git bisect good b976690f5db26fbc7c2be413bfa0fbd270547a94  # 00:10  G    305     0    5   5  x86/mm/pti: Introduce pti_finalize()
> git bisect good 9bae3197e15dd5e03ce8e237db6fe4486b08a775  # 00:49  G    308     0    3   4  x86/ldt: Split out sanity check in map_ldt_struct()
> git bisect  bad 5e8105950a8b3e03e805299b4d05020ee4eda31a  # 01:12  B    131     1    4   4  x86/mm/pti: Add Warning when booting on a PCID capable CPU
> git bisect good 6df934b92a549cb3badb6d576f71aeb133e2f110  # 01:47  G    310     0    7  10  x86/ldt: Enable LDT user-mapping for PAE
> git bisect  bad 7757d607c6b31867777de42e1fb0210b9c5d8b70  # 02:08  B    134     1    2   2  x86/pti: Allow CONFIG_PAGE_TABLE_ISOLATION for x86_32
> # first bad commit: [7757d607c6b31867777de42e1fb0210b9c5d8b70] x86/pti: Allow CONFIG_PAGE_TABLE_ISOLATION for x86_32
> git bisect good 6df934b92a549cb3badb6d576f71aeb133e2f110  # 03:14  G    900     0    9  19  x86/ldt: Enable LDT user-mapping for PAE
> # extra tests on HEAD of tip/x86/pti
> git bisect  bad 8c934e01a7ce685d98e970880f5941d79272c654  # 03:15  B    279     2    0   6  x86/pti: Check the return value of pti_user_pagetable_walk_pmd()
> # extra tests on tree/branch tip/x86/pti
> git bisect  bad 8c934e01a7ce685d98e970880f5941d79272c654  # 03:20  B    279     2    0   6  x86/pti: Check the return value of pti_user_pagetable_walk_pmd()
> # extra tests with first bad commit reverted
> git bisect good 90d0ce801fac8115d424e40a4a258aeed0e409dd  # 03:58  G    302     0    7   7  Revert "x86/pti: Allow CONFIG_PAGE_TABLE_ISOLATION for x86_32"
> # extra tests on tree/branch tip/master
> git bisect  bad 4edd5aa38cec47346e0d0a85fa43964828b982d0  # 04:37  B    257     1    5   6  Merge branch 'linus'

May I ask how this was bisected? I found it very hard to reproduce, it
triggered less then two times a day with the attached reproducer. Given
that the report came pretty fast after the patches landed in
tip/x86/pti, I guess it triggered a lot faster in your testing.

Regards,

	Joerg