On Fri, Aug 07, 2026 at 04:24:00PM +0100, Muhammad Usama Anjum wrote: > On 07/08/2026 8:09 am, Alexander Gordeev wrote: > > On Thu, Aug 06, 2026 at 09:38:39AM +0100, Muhammad Usama Anjum wrote: > >> pte_t is used both for logical PTE values and for entries stored in a PTE > >> table, so pte_t * does not distinguish a pointer to a copied value from a > >> pointer to table storage. > >> > >> Introduce hw_pte_t as the generic name for a PTE table element. Define it > >> as a macro alias of pte_t by default. When an architecture selects > >> ARCH_HAS_HW_PTE_T, define it as a structure containing a pte_t instead. > >> This preserves the representation while allowing converted architectures > >> to enforce the distinction at compile time. > >> > >> Keep the C type definitions behind an __ASSEMBLY__ check because > >> architecture assembly sources can include this header indirectly. Include > >> asm/page.h so consumers such as linux/vmalloc.h retain the page definitions > >> they previously obtained from that header. > >> > >> Signed-off-by: Muhammad Usama Anjum <[email protected]> > >> --- > >> Changes since RFC v1: > >> - Add the ARCH_HAS_HW_PTE_T opt-in and generic wrapper definition. > >> - Exclude the C type definitions from assembly sources. > >> - Update the description for the new opt-in model. > >> --- > >> MAINTAINERS | 1 + > >> include/linux/pgtable_types.h | 17 +++++++++++++++++ > >> mm/Kconfig | 3 +++ > >> 3 files changed, 21 insertions(+) > >> create mode 100644 include/linux/pgtable_types.h > >> > >> diff --git a/MAINTAINERS b/MAINTAINERS > >> index e9c8567308a75..7169bea968cf5 100644 > >> --- a/MAINTAINERS > >> +++ b/MAINTAINERS > >> @@ -16982,6 +16982,7 @@ F: include/linux/mmu_notifier.h > >> F: include/linux/pagewalk.h > >> F: include/linux/pgalloc.h > >> F: include/linux/pgtable.h > >> +F: include/linux/pgtable_types.h > >> F: include/linux/ptdump.h > >> F: include/linux/vmpressure.h > >> F: include/linux/vmstat.h > >> diff --git a/include/linux/pgtable_types.h b/include/linux/pgtable_types.h > >> new file mode 100644 > >> index 0000000000000..70c3edd00a01b > >> --- /dev/null > >> +++ b/include/linux/pgtable_types.h > >> @@ -0,0 +1,17 @@ > >> +/* SPDX-License-Identifier: GPL-2.0 */ > >> +#ifndef _LINUX_PGTABLE_TYPES_H > >> +#define _LINUX_PGTABLE_TYPES_H > >> + > >> +#include <asm/page.h> > >> + > >> +#ifndef __ASSEMBLY__ > >> + > >> +#ifdef CONFIG_ARCH_HAS_HW_PTE_T > >> +typedef struct { pte_t __pte; } hw_pte_t; > > > > On s390 it fails to compile once we do typedef hw_pte_t *pgtable_t > > in asm/page.h. m68k, powerpc and sparc may also have such problem. > > > > The below declaration helps to resolve it using forward declaration > > and without meddling with headers, though I do not like it much: > > > > typedef struct __hw_pte_t { pte_t __pte; } hw_pte_t; > Thank you for testing it out on s390. > > As __hw_pte_t isn't being used yet in this series, would s390 enablement > patches add __hw_pte_t to this definition?
I hope there is a better solution. As I noted m68k, powerpc and sparc may also be affected, so I would suggest to look into those as well. I would prefer s390 to use the generic one rather than circumvent a compile error in a custom way. > This could have been avoided if each architecture defined its own hw_pte_t. > But for now we are keeping the generic definition of hw_pte_t. > > > > >> +#else > >> +#define hw_pte_t pte_t > >> +#endif > >> + > >> +#endif /* !__ASSEMBLY__ */ > >> + > >> +#endif /* _LINUX_PGTABLE_TYPES_H */ > >> diff --git a/mm/Kconfig b/mm/Kconfig > >> index 331daf7fcfab5..31ba9ebf4aafd 100644 > >> --- a/mm/Kconfig > >> +++ b/mm/Kconfig > >> @@ -1316,6 +1316,9 @@ comment "GUP_TEST needs to have DEBUG_FS enabled" > >> config GUP_GET_PXX_LOW_HIGH > >> bool > >> > >> +config ARCH_HAS_HW_PTE_T > >> + bool > >> + > >> config DMAPOOL_TEST > >> tristate "Enable a module to run time tests on dma_pool" > >> depends on HAS_DMA > >> -- > >> 2.47.3 > >> > > -- > Thanks, > Usama >
