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From: Uros Bizjak <ubizjak@gmail.com>
Date: Mon, 25 Mar 2024 11:31:40 +0100
Message-ID: <CAFULd4bFbhOQ+mx2=pKqLbLznR-UFZamS4HhdUYZF2qFKNcDVg@mail.gmail.com>
Subject: Re: [linus:master] [x86/percpu] ca42563486: BUG:unable_to_handle_page_fault_for_address
To: kernel test robot <oliver.sang@intel.com>
Cc: oe-lkp@lists.linux.dev, lkp@intel.com, linux-kernel@vger.kernel.org, 
	Ingo Molnar <mingo@kernel.org>, Nadav Amit <namit@vmware.com>, Andy Lutomirski <luto@kernel.org>, 
	Brian Gerst <brgerst@gmail.com>, Denys Vlasenko <dvlasenk@redhat.com>, 
	"H. Peter Anvin" <hpa@zytor.com>, Linus Torvalds <torvalds@linux-foundation.org>, 
	Peter Zijlstra <peterz@infradead.org>, Thomas Gleixner <tglx@linutronix.de>, 
	Josh Poimboeuf <jpoimboe@redhat.com>, linux-mm@kvack.org
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On Mon, Mar 25, 2024 at 9:50=E2=80=AFAM kernel test robot <oliver.sang@inte=
l.com> wrote:
>
>
> hi, Uros Bizjak,
>
> we reported an early crash issue for this commit last Oct.
> https://lore.kernel.org/all/202310071301.a5113890-oliver.sang@intel.com/
>
> as you mentioned at that time
> "It is KASAN that is not compatible with named address spaces [1]."
>
> now we noticed the commit is merged into mainline, and we observed a diff=
erent
> issue related with kcsan_setup_watchpoint. below detail report FYI.
>
> [1] https://lore.kernel.org/lkml/CAHk-=3Dwi6U-O1wdPOESuCE6QO2OaPu0hEzaig0=
uDOU4L5CREhug@mail.gmail.com/
>

Yes, it is the same issue, but with KCSAN.

> Hello,
>
> kernel test robot noticed "BUG:unable_to_handle_page_fault_for_address" o=
n:
>
> commit: ca4256348660cb2162668ec3d13d1f921d05374a ("x86/percpu: Use C for =
percpu read/write accessors")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
>
> [test failed on linus/master b3603fcb79b1036acae10602bffc4855a4b9af80]
> [test failed on linux-next/master 226d3c72fcde130a99d760895ebdd20e78e02cb=
5]
>
> in testcase: boot
>
> compiler: gcc-12
> test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 1=
6G

We already have the candidate fix for GCC [1], the fix will be in gcc-13.3+=
.

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111736

Please find attached an emergency patch for mainline that disables
named address spaces when KCSAN is enabled. I'll post a formal patch
submission in a moment. The named AS will be re-enabled with KCSAN
with a patch via -tip tree.

Thanks,
Uros.

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