Re: [PATCH 1/2] arm64: mm: drop VM_FAULT_BADMAP/VM_FAULT_BADACCESS

[Aishwarya TCV <aishwarya.tcv@arm.com>]

On 07/04/2024 09:12, Kefeng Wang wrote:
> If bad map or access, directly set si_code to SEGV_MAPRR or SEGV_ACCERR,
> also set fault to 0 and goto error handling, which make us to drop the
> arch's special vm fault reason.
> 
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---
>  arch/arm64/mm/fault.c | 41 ++++++++++++++++++-----------------------
>  1 file changed, 18 insertions(+), 23 deletions(-)

Hi Kefeng,

While running LTP test suite, I observed that few test cases are unable
to kill exe when run against next-master(next-20240409) kernel with
Arm64 on JUNO in our CI. I can send the full logs if required, but it
doesn't say much.

A bisect identified cf0049a15207a5a78798105eff789c2025bcf652 as the
first bad commit. Bisected it on the tag "next-20240409" at repo
"https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git".

This works fine on Linux version v6.9-rc3

Here are some of the failing test cases in LTP quickhit:
-----------------------------
chdir01
link04
select03
unlink07


Failure log:
-----------
06:06:49.288908  Test timeouted, sending SIGKILL!
06:06:54.293806  Test timeouted, sending SIGKILL!
06:06:59.296872  Test timeouted, sending SIGKILL!
06:07:04.292044  Test timeouted, sending SIGKILL!
06:07:09.290185  Test timeouted, sending SIGKILL!
06:07:14.295134  Test timeouted, sending SIGKILL!
06:07:19.293279  Test timeouted, sending SIGKILL!
06:07:24.292405  Test timeouted, sending SIGKILL!
06:07:24.292790  Cannot kill test processes!
06:07:24.296564  Congratulation, likely test hit a kernel bug.
06:07:24.301315  Exiting uncleanly...


Bisect log:
----------
git bisect start
# good: [fec50db7033ea478773b159e0e2efb135270e3b7] Linux 6.9-rc3
git bisect good fec50db7033ea478773b159e0e2efb135270e3b7
# bad: [a053fd3ca5d1b927a8655f239c84b0d790218fda] Add linux-next
specific files for 20240409
git bisect bad a053fd3ca5d1b927a8655f239c84b0d790218fda
# bad: [4eb0063b031ea720cd8971e3e3d2426d27c5d7a6] Merge branch
'mtd/next' of git://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git
git bisect bad 4eb0063b031ea720cd8971e3e3d2426d27c5d7a6
# bad: [24dde11bfadd5f38c6cca3cea6f16971bd10dc86] Merge branch
'for-next' of git://github.com/Xilinx/linux-xlnx.git
git bisect bad 24dde11bfadd5f38c6cca3cea6f16971bd10dc86
# bad: [bef23348d7e75c502399ba1a24627aa447b816dc] Merge branch
'mm-everything' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
git bisect bad bef23348d7e75c502399ba1a24627aa447b816dc
# good: [3317f7faabc24b500c26d02615ac75ca2786e272] mm: swap:
free_swap_and_cache_nr() as batched free_swap_and_cache()
git bisect good 3317f7faabc24b500c26d02615ac75ca2786e272
# good: [541970e62546ff5c96622669f2796d43b1a406e3] Merge branch
'gpio/for-current' of
git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux.git
git bisect good 541970e62546ff5c96622669f2796d43b1a406e3
# bad: [1df265717e0f9d96079073189f6e6c52a48e493c]
__mod_memcg_lruvec_state-enhance-diagnostics-fix
git bisect bad 1df265717e0f9d96079073189f6e6c52a48e493c
# bad: [19ab4054346474c2b456f9bff6a98e41e5e46224] hugetlb: Simplify
hugetlb_wp() arguments
git bisect bad 19ab4054346474c2b456f9bff6a98e41e5e46224
# good: [75ef450aa9828ca20817c46c5b99f131156f6eee] x86: mm: accelerate
pagefault when badaccess
git bisect good 75ef450aa9828ca20817c46c5b99f131156f6eee
# bad: [c6b5a19e679bb713efd57d82f9080f780e0bb60a] mm/treewide: rename
CONFIG_HAVE_FAST_GUP to CONFIG_HAVE_GUP_FAST
git bisect bad c6b5a19e679bb713efd57d82f9080f780e0bb60a
# bad: [01446d1e9e627945664f2a1daa53e8720946d0cd] mm: remove struct page
from get_shadow_from_swap_cache
git bisect bad 01446d1e9e627945664f2a1daa53e8720946d0cd
# bad: [8f9d6a30dd992c44debea3161083a6c2cd3ad87f] arm: mm: drop
VM_FAULT_BADMAP/VM_FAULT_BADACCESS
git bisect bad 8f9d6a30dd992c44debea3161083a6c2cd3ad87f
# bad: [cf0049a15207a5a78798105eff789c2025bcf652] arm64: mm: drop
VM_FAULT_BADMAP/VM_FAULT_BADACCESS
git bisect bad cf0049a15207a5a78798105eff789c2025bcf652
# first bad commit: [cf0049a15207a5a78798105eff789c2025bcf652] arm64:
mm: drop VM_FAULT_BADMAP/VM_FAULT_BADACCESSgit bisect log


Thanks,
Aishwarya