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

[David Hildenbrand (Arm)]

On 11/3/26 16:43, Andrew Morton wrote:
> On Tue, 3 Nov 2026 13:26:47 +0100 Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> 
>> 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().
>>
>> --- 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;
>>  
> 
> (cc Dave)
> 
> fwiw this was discussed a couple of years ago but nothing really came
> of it.
> 
> https://lore.kernel.org/20240401185451.6897208962d3fc47a12ffb5a@xxxxxxxx

IIUC Usama has some things in the works that will avoid on-stack pmds.

-- 
Cheers,

David