Re: [linus:master] [atomic] 80047d84ee: WARNING:at_include/linux/instrumented.h:#__split_huge_pmd_locked

[Peter Zijlstra <peterz@infradead.org>]

On Tue, Nov 03, 2026 at 08:58:07AM +0800, kernel test robot wrote:
> 
> 
> Hello,
> 
> kernel test robot noticed "WARNING:at_include/linux/instrumented.h:#__split_huge_pmd_locked" on:
> 
> commit: 80047d84eed25e9c92cfb9169980a0dfec110246 ("atomic: add alignment check to instrumented atomic operations") https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> 
> [test failed on linux-next/master 7649ba73f9e7e1e04d0b46213e39c79ae09dd55c]
> 
> in testcase: trinity
> with following parameters:
> 
> 	runtime: 300s
> 	group: group-02
> 	nr_groups: 5
> 
> 
> config: i386-randconfig-1005-20261101
> compiler: gcc-14
> test machine: qemu-system-i386 -enable-kvm -cpu Icelake-Server-noTSX,enforce,lm=off -smp 4 -m 4G
> 
> (please refer to attached dmesg/kmsg for entire log/backtrace)
> 
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <yi1.lai@intel.com>
> | Closes: https://lore.kernel.org/oe-lkp/202611022259.def3e086-lkp@intel.com
> 
> 
> [   18.704659][ T3738] ------------[ cut here ]------------
> [   18.706815][ T3738] WARNING: include/linux/instrumented.h:62 at __split_huge_pmd_locked+0x6d2/0xac0, CPU#0: trinity-c1/3738
> [   18.717796][ T3738] Modules linked in:
> [   18.719286][ T3738] CPU: 0 UID: 65534 PID: 3738 Comm: trinity-c1 Not tainted 6.19.0-rc6-00100-g80047d84eed2 #1 PREEMPT(lazy)
> [   18.723193][ T3738] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
> [   18.726644][ T3738] EIP: __split_huge_pmd_locked (x86/include/asm/pgtable.h:228 (discriminator 1) huge_memory.c:3128 (discriminator 1))
> [   18.728717][ T3738] Code: dc 85 d2 75 0c c6 45 c2 00 85 c0 0f 84 ee fe ff ff f6 45 bc 03 0f 85 47 03 00 00 8b 45 bc 80 08 10 c6 45 c2 01 e9 d5 fe ff ff <0f> 0b 0f c7 4d ec 0f 84 34 fd ff ff eb f2 e8 db 58 40 01 85 c0 0f
> All code
> ========
>    0:	dc 85 d2 75 0c c6    	faddl  -0x39f38a2e(%rbp)
>    6:	45 c2 00 85          	rex.RB ret $0x8500
>    a:	c0 0f 84             	rorb   $0x84,(%rdi)
>    d:	ee                   	out    %al,(%dx)
>    e:	fe                   	(bad)
>    f:	ff                   	(bad)
>   10:	ff f6                	push   %rsi
>   12:	45 bc 03 0f 85 47    	rex.RB mov $0x47850f03,%r12d
>   18:	03 00                	add    (%rax),%eax
>   1a:	00 8b 45 bc 80 08    	add    %cl,0x880bc45(%rbx)
>   20:	10 c6                	adc    %al,%dh
>   22:	45 c2 01 e9          	rex.RB ret $0xe901
>   26:	d5 fe ff ff          	{rex2 0xfe} ud0 %r23,%r31
>   2a:*	0f 0b                	ud2		<-- trapping instruction
>   2c:	0f c7 4d ec          	cmpxchg8b -0x14(%rbp)
>   30:	0f 84 34 fd ff ff    	je     0xfffffffffffffd6a
>   36:	eb f2                	jmp    0x2a

AFAICT this is pxx_xchg64() from the PAE code operating on an on-stack
pmd value.

The below 'fixes' it, but the question is of course, WTF are we using an
on-stack pmd value for set_pmd().


---

diff --git a/arch/x86/include/asm/pgtable-3level_types.h b/arch/x86/include/asm/pgtable-3level_types.h
index 580b09bf6a45..b1343a1dc55a 100644
--- a/arch/x86/include/asm/pgtable-3level_types.h
+++ b/arch/x86/include/asm/pgtable-3level_types.h
@@ -5,12 +5,12 @@
 #ifndef __ASSEMBLER__
 #include <linux/types.h>
 
-typedef u64	pteval_t;
-typedef u64	pmdval_t;
-typedef u64	pudval_t;
-typedef u64	p4dval_t;
-typedef u64	pgdval_t;
-typedef u64	pgprotval_t;
+typedef u64 __aligned(8)	pteval_t;
+typedef u64 __aligned(8)	pmdval_t;
+typedef u64 __aligned(8)	pudval_t;
+typedef u64 __aligned(8)	p4dval_t;
+typedef u64 __aligned(8)	pgdval_t;
+typedef u64 __aligned(8)	pgprotval_t;
 
 typedef union {
 	struct {