On 17/09/2024 11:20, David Hildenbrand wrote:
On 17.09.24 09:31, Anshuman Khandual wrote:This changes platform's pmd_val() to access the pmd_t element directly like other architectures rather than current pointer address based dereferencing that prevents transition into pmdp_get(). Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> Cc: Guo Ren <guoren@xxxxxxxxxx> Cc: Arnd Bergmann <arnd@xxxxxxxx> Cc: linux-m68k@xxxxxxxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx> --- arch/m68k/include/asm/page.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/m68k/include/asm/page.h b/arch/m68k/include/asm/page.h index 8cfb84b49975..be3f2c2a656c 100644 --- a/arch/m68k/include/asm/page.h +++ b/arch/m68k/include/asm/page.h @@ -19,7 +19,7 @@ */ #if !defined(CONFIG_MMU) || CONFIG_PGTABLE_LEVELS == 3 typedef struct { unsigned long pmd; } pmd_t; -#define pmd_val(x) ((&x)->pmd) +#define pmd_val(x) ((x).pmd) #define __pmd(x) ((pmd_t) { (x) } ) #endifTrying to understand what's happening here, I stumbled over commit ef22d8abd876e805b604e8f655127de2beee2869 Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Date: Fri Jan 31 13:45:36 2020 +0100 m68k: mm: Restructure Motorola MMU page-table layout The Motorola 68xxx MMUs, 040 (and later) have a fixed 7,7,{5,6} page-table setup, where the last depends on the page-size selected (8k vs 4k resp.), and head.S selects 4K pages. For 030 (and earlier) we explicitly program 7,7,6 and 4K pages in %tc. However, the current code implements this mightily weird. What it does is group 16 of those (6 bit) pte tables into one 4k page to not waste space. The down-side is that that forces pmd_t to be a 16-tuple pointing to consecutive pte tables. This breaks the generic code which assumes READ_ONCE(*pmd) will be word sized. Where we did #if !defined(CONFIG_MMU) || CONFIG_PGTABLE_LEVELS == 3 -typedef struct { unsigned long pmd[16]; } pmd_t; -#define pmd_val(x) ((&x)->pmd[0]) -#define __pmd(x) ((pmd_t) { { (x) }, }) +typedef struct { unsigned long pmd; } pmd_t; +#define pmd_val(x) ((&x)->pmd) +#define __pmd(x) ((pmd_t) { (x) } ) #endif So I assume this should be fine
I think you're implying that taking the address then using arrow operator was needed when pmd was an array? I don't really understand that if so? Surely: ((x).pmd[0]) would have worked too? I traced back further, and a version of that macro exists with the "address of" and arrow operator since the beginning of (git) time.
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
