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 02:41:32PM +0100, Arnd Bergmann wrote:

> FWIW, I checked the other architectures that may be affected:
> 
> - 32-bit arm has transparent hugepages and a 64-bit pmd_t with lpae,
>   but that type has natural alignment, and pmd_populate is a
>   simple assignment.
> 
> - arc has transparent hugepages and a 32-bit pmd_t but a 64-bit
>   pte_t that is not naturally aligned. It probably should be
>   aligned, even though I don't see any actual bugs
> 
> - sh has a 64-bit pmd_t on sh4a CPUs that is not naturally
>   aligned and probably should be, but there are no transparent
>   hugepages.
> 
> All other 32-bit targets don't use transparent hugepages
> or 64-bit pmd_t. 
> 
> We probably only need to align p?d_t though, not p?dval_t.
> How about the version below?
> 
>     Arnd
> 
> diff --git a/arch/arc/include/asm/page.h b/arch/arc/include/asm/page.h
> index 9720fe6b2c24..af5303459d56 100644
> --- a/arch/arc/include/asm/page.h
> +++ b/arch/arc/include/asm/page.h
> @@ -65,7 +65,7 @@ typedef struct {
>  
>  typedef struct {
>  #ifdef CONFIG_ARC_HAS_PAE40
> -	unsigned long long pte;
> +	unsigned long long pte __aligned(8);
>  #else
>  	unsigned long pte;
>  #endif
> diff --git a/arch/sh/include/asm/pgtable-3level.h b/arch/sh/include/asm/pgtable-3level.h
> index d1ce73f3bd85..6d5e2e3248f2 100644
> --- a/arch/sh/include/asm/pgtable-3level.h
> +++ b/arch/sh/include/asm/pgtable-3level.h
> @@ -33,7 +33,7 @@ typedef union {
>  		unsigned long pmd_low;
>  		unsigned long pmd_high;
>  	};
> -	unsigned long long pmd;
> +	unsigned long long pmd __aligned(8);
>  } pmd_t;
>  #define pmd_val(x)	((x).pmd)
>  #define __pmd(x)	((pmd_t) { .pmd = (x) } )
> diff --git a/arch/x86/include/asm/pgtable-3level_types.h b/arch/x86/include/asm/pgtable-3level_types.h
> index 580b09bf6a45..061283293341 100644
> --- a/arch/x86/include/asm/pgtable-3level_types.h
> +++ b/arch/x86/include/asm/pgtable-3level_types.h
> @@ -16,14 +16,14 @@ typedef union {
>  	struct {
>  		unsigned long pte_low, pte_high;
>  	};
> -	pteval_t pte;
> +	pteval_t pte __aligned(8);
>  } pte_t;
>  
>  typedef union {
>  	struct {
>  		unsigned long pmd_low, pmd_high;
>  	};
> -	pmdval_t pmd;
> +	pmdval_t pmd __aligned(8);
>  } pmd_t;
>  #endif	/* !__ASSEMBLER__ */
>  
> diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
> index 2ec250ba467e..5c028b3f59c4 100644
> --- a/arch/x86/include/asm/pgtable_types.h
> +++ b/arch/x86/include/asm/pgtable_types.h
> @@ -292,7 +292,7 @@ enum page_cache_mode {
>  
>  typedef struct pgprot { pgprotval_t pgprot; } pgprot_t;
>  
> -typedef struct { pgdval_t pgd; } pgd_t;
> +typedef struct { pgdval_t pgd __aligned(sizeof(pgdval_t)); } pgd_t;
>  
>  static inline pgprot_t pgprot_nx(pgprot_t prot)
>  {

This doesn't cover all of p?d_t, does it?