linux-kernel - Re: [linus:master] [x86/percpu] ca42563486: BUG:unable_to_handle_page_fault_for

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Date: Wed, 27 Mar 2024 10:27:10 +0800
From: Oliver Sang <oliver.sang@...el.com>
To: Uros Bizjak <ubizjak@...il.com>
CC: <oe-lkp@...ts.linux.dev>, <lkp@...el.com>, <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>, Nadav Amit <namit@...are.com>, "Andy
 Lutomirski" <luto@...nel.org>, Brian Gerst <brgerst@...il.com>, Denys
 Vlasenko <dvlasenk@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, Linus
 Torvalds <torvalds@...ux-foundation.org>, Peter Zijlstra
	<peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>, Josh Poimboeuf
	<jpoimboe@...hat.com>, <linux-mm@...ck.org>, <oliver.sang@...el.com>
Subject: Re: [linus:master] [x86/percpu] ca42563486:
 BUG:unable_to_handle_page_fault_for_address

hi, Uros Bizjak,

On Mon, Mar 25, 2024 at 11:31:40AM +0100, Uros Bizjak wrote:
> On Mon, Mar 25, 2024 at 9:50 AM kernel test robot <oliver.sang@...el.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 different
> > issue related with kcsan_setup_watchpoint. below detail report FYI.
> >
> > [1] https://lore.kernel.org/lkml/CAHk-=wi6U-O1wdPOESuCE6QO2OaPu0hEzaig0uDOU4L5CREhug@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" on:
> >
> > 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 226d3c72fcde130a99d760895ebdd20e78e02cb5]
> >
> > in testcase: boot
> >
> > compiler: gcc-12
> > test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
> 
> 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=111736
> 
> 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 a lot for information! we will apply this patch.

> 
> Thanks,
> Uros.

> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 39886bab943a..4fff6ed46e90 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2439,6 +2439,8 @@ config USE_X86_SEG_SUPPORT
>  	# with named address spaces - see GCC PR sanitizer/111736.
>  	#
>  	depends on !KASAN
> +	# -fsanitize=thread (KCSAN) is also incompatible.
> +	depends on !KCSAN
>  
>  config CC_HAS_SLS
>  	def_bool $(cc-option,-mharden-sls=all)