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Fri, 7 Aug 2026 07:09:12 +0000 (GMT) Date: Fri, 7 Aug 2026 09:09:11 +0200 From: Alexander Gordeev To: Muhammad Usama Anjum Cc: Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Simona Vetter , Dimitri Sivanich , Arnd Bergmann , Greg Kroah-Hartman , "James E.J. Bottomley" , Helge Deller , Juergen Gross , Stefano Stabellini , Muchun Song , Oscar Salvador , Andrew Morton , "Liam R. Howlett" , Lorenzo Stoakes , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , Andrey Ryabinin , David Hildenbrand , Pasha Tatashin , Chris Li , Kairui Song , Uladzislau Rezki , Steven Rostedt , Masami Hiramatsu , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , SJ Park , "Matthew Wilcox (Oracle)" , Jan Kara , Jason Gunthorpe , Leon Romanovsky , Miaohe Lin , Dennis Zhou , Tejun Heo , Christoph Lameter , Mike Rapoport , Johannes Weiner , ziy@nvidia.com, pfalcato@suse.de, ryan.roberts@arm.com, linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-parisc@vger.kernel.org, xen-devel@lists.xenproject.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, kasan-dev@googlegroups.com, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, damon@lists.linux.dev Subject: Re: [PATCH 1/9] mm: introduce hw_pte_t for PTE table storage Message-ID: <3db8233c-3785-444e-b2eb-3e5fc5cb2f17-agordeev@linux.ibm.com> References: <20260806083926.1807279-1-usama.anjum@arm.com> <20260806083926.1807279-2-usama.anjum@arm.com> MIME-Version: 1.0 Content-Type: text/plain; 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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 > --- > 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 > + > +#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; > +#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 >