kernel/git/next/linux-next.git/arch/m68k/Kconfig, branch master

mm: make userland page table freeing RCU-safe

2026-09-20T16:19:42+00:00

Now every architecture has been converted to support CONFIG_MMU_GATHER_RCU_TABLE_FREE, this configuration option no longer makes any sense to keep around. Therefore remove it, and remove all the dead code that existed for !CONFIG_MMU_GATHER_RCU_TABLE_FREE architectures previously. Additionally, CONFIG_MMU_GATHER_TABLE_FREE is no longer necessary, as all architectures instead use CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE when a custom __tlb_remove_table() is required, so remove this too. A number of architectures only enabled CONFIG_MMU_GATHER_RCU_TABLE_FREE if CONFIG_MMU was set, however the mmu_gather logic only actually does something meaningful if CONFIG_MMU is set (mmu_gather.c is only compiled in this case, for instance). As a result, there's no need to gate any of this logic on CONFIG_MMU explicitly. CONFIG_PT_RECLAIM however does have a strict dependency on CONFIG_MMU, so make this dependency explicit. Additionally, correct comments to remove references to non-RCU page table gathering and make it clear that this is not 'semi-RCU', nor has it been since commit 1fb3d8c20bfa ("mm/mmu_gather: replace IPI with synchronize_rcu() when batch allocation fails"). With this change in place the kernel policy is now that userspace page tables are freed after an RCU grace period, and thus it is now safe to unconditionally perform page table walks under RCU, safe in the knowledge that page tables will not be freed underneath the walker. This is all that is guaranteed, however, so naturally it is still incumbent upon page table walkers to ensure that the page table entries are as expected. Link: https://lore.kernel.org/20260911-rcu-pagetable-freeing-v3-11-7b8c86103821@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Signed-off-by: Andrew Morton Acked-by: Kiryl Shutsemau (Meta) Cc: Albert Ou Cc: Alexander Gordeev Cc: Alexandre Ghiti Cc: Andreas Larsson Cc: "Aneesh Kumar K.V" Cc: Anton Ivanov Cc: Arnd Bergmann Cc: Baolin Wang Cc: Barry Song Cc: "Borislav Petkov (AMD)" Cc: Catalin Marinas Cc: Christian Borntraeger Cc: Christian Zankel Cc: Dave Hansen Cc: David Hildenbrand Cc: David S. Miller Cc: Dev Jain Cc: Dinh Nguyen Cc: Geert Uytterhoeven Cc: Guo Ren Cc: Heiko Carstens Cc: Helge Deller Cc: "H. Peter Anvin" Cc: Huacai Chen Cc: Hugh Dickins Cc: Ingo Molnar Cc: James Bottomley Cc: Jason Gunthorpe Cc: Johannes Berg Cc: John Hubbard Cc: John Paul Adrian Glaubitz Cc: Jonas Bonn Cc: Lance Yang Cc: Liam R. Howlett Cc: Madhavan Srinivasan Cc: Magnus Lindholm Cc: Marc Rutland Cc: Matt Turner Cc: Max Filippov Cc: Michael Ellerman Cc: Michal Hocko Cc: Michal Simek Cc: Mike Rapoport Cc: Nicholas Piggin Cc: Palmer Dabbelt Cc: Peter Xu Cc: Peter Zijlstra Cc: Richard Henderson Cc: Richard Weinberger Cc: Rich Felker Cc: Russell King Cc: Ryan Roberts Cc: Stafford Horne Cc: Stefan Kristiansson Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Bogendoerfer Cc: Vasily Gorbik Cc: Vineet Gupta Cc: Vlastimil Babka Cc: WANG Xuerui Cc: Will Deacon Cc: Yoshinori Sato Cc: Zi Yan

mm: enable MMU_GATHER_RCU_TABLE_FREE for m68k-motorola

2026-09-20T16:19:41+00:00

sun3 and coldfire are already supported, however motorola requires a little more care. Here, custom table removal logic is required, so CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE is enabled for m68k-motorola. Firstly as part of this change, the page table level must be communicated to the underlying __tlb_remove_table() implementation. Take advantage of the fact that page tables are aligned by more than enough to permit setting TABLE_PTE or TABLE_PMD in the low bits of the pointer, and store this there. Then update __pte_free_tlb() and __pmd_free_tlb() to pass this through, then have __tlb_remove_table() decode this and pass it to free_pointer_table(). The page table freeing is performed via call_rcu(), so free_pointer_table() now will be invoked from softirq context, and as such may be re-entrant. Introduce an irq save/restore spinlock to handle this, and hold it over the time a given ptable entry is being referenced in both get_pointer_table() and free_pointer_table(). In order to make things a little easier in this respect, separate out the logic for adding a new ptable entry into add_pointer_table() and only hold the lock during ptable entry insertion in this case. Note that original list_add_tail(new, dp) added new prior to dp, which is ptable_list[type].next, i.e. after ptable_list[type]. The equivalent therefore is list_add(new, &ptable_list[type]), which adds new after ptable_list[type], only without needing to make reference to dp. Note that, as m68k-motorola specifies CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE, it does not enable CONFIG_PT_RECLAIM. This isn't meaningfully impactful. With this applied, all of m68k implements CONFIG_MMU_GATHER_RCU_TABLE_FREE. This forms part of an overall effort to switch every architecture to this mode. Link: https://lore.kernel.org/20260911-rcu-pagetable-freeing-v3-9-7b8c86103821@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Signed-off-by: Andrew Morton Acked-by: Kiryl Shutsemau (Meta) Cc: Albert Ou Cc: Alexander Gordeev Cc: Alexandre Ghiti Cc: Andreas Larsson Cc: "Aneesh Kumar K.V" Cc: Anton Ivanov Cc: Arnd Bergmann Cc: Baolin Wang Cc: Barry Song Cc: "Borislav Petkov (AMD)" Cc: Catalin Marinas Cc: Christian Borntraeger Cc: Christian Zankel Cc: Dave Hansen Cc: David Hildenbrand Cc: David S. Miller Cc: Dev Jain Cc: Dinh Nguyen Cc: Geert Uytterhoeven Cc: Guo Ren Cc: Heiko Carstens Cc: Helge Deller Cc: "H. Peter Anvin" Cc: Huacai Chen Cc: Hugh Dickins Cc: Ingo Molnar Cc: James Bottomley Cc: Jason Gunthorpe Cc: Johannes Berg Cc: John Hubbard Cc: John Paul Adrian Glaubitz Cc: Jonas Bonn Cc: Lance Yang Cc: Liam R. Howlett Cc: Madhavan Srinivasan Cc: Magnus Lindholm Cc: Marc Rutland Cc: Matt Turner Cc: Max Filippov Cc: Michael Ellerman Cc: Michal Hocko Cc: Michal Simek Cc: Mike Rapoport Cc: Nicholas Piggin Cc: Palmer Dabbelt Cc: Peter Xu Cc: Peter Zijlstra Cc: Richard Henderson Cc: Richard Weinberger Cc: Rich Felker Cc: Russell King Cc: Ryan Roberts Cc: Stafford Horne Cc: Stefan Kristiansson Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Bogendoerfer Cc: Vasily Gorbik Cc: Vineet Gupta Cc: Vlastimil Babka Cc: WANG Xuerui Cc: Will Deacon Cc: Yoshinori Sato Cc: Zi Yan

mm: enable MMU_GATHER_RCU_TABLE_FREE for m68k-coldfire

2026-09-20T16:19:41+00:00

Similar to sun3, the coldfire variant of m68k uses 2-level page tables. Update its __pte_free_tlb() function to use tlb_remove_ptdesc() in order that, with CONFIG_MMU_GATHER_RCU_TABLE_FREE, page tables are freed under RCU. The page tables occupy a page each and have no odd semantics, so this change suffices to allow enabling of CONFIG_MMU_GATHER_RCU_TABLE_FREE for m68k-coldfire, so do so. This forms part of an overall effort to switch every architecture to this mode. Link: https://lore.kernel.org/20260911-rcu-pagetable-freeing-v3-7-7b8c86103821@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Signed-off-by: Andrew Morton Acked-by: Kiryl Shutsemau (Meta) Cc: Albert Ou Cc: Alexander Gordeev Cc: Alexandre Ghiti Cc: Andreas Larsson Cc: "Aneesh Kumar K.V" Cc: Anton Ivanov Cc: Arnd Bergmann Cc: Baolin Wang Cc: Barry Song Cc: "Borislav Petkov (AMD)" Cc: Catalin Marinas Cc: Christian Borntraeger Cc: Christian Zankel Cc: Dave Hansen Cc: David Hildenbrand Cc: David S. Miller Cc: Dev Jain Cc: Dinh Nguyen Cc: Geert Uytterhoeven Cc: Guo Ren Cc: Heiko Carstens Cc: Helge Deller Cc: "H. Peter Anvin" Cc: Huacai Chen Cc: Hugh Dickins Cc: Ingo Molnar Cc: James Bottomley Cc: Jason Gunthorpe Cc: Johannes Berg Cc: John Hubbard Cc: John Paul Adrian Glaubitz Cc: Jonas Bonn Cc: Lance Yang Cc: Liam R. Howlett Cc: Madhavan Srinivasan Cc: Magnus Lindholm Cc: Marc Rutland Cc: Matt Turner Cc: Max Filippov Cc: Michael Ellerman Cc: Michal Hocko Cc: Michal Simek Cc: Mike Rapoport Cc: Nicholas Piggin Cc: Palmer Dabbelt Cc: Peter Xu Cc: Peter Zijlstra Cc: Richard Henderson Cc: Richard Weinberger Cc: Rich Felker Cc: Russell King Cc: Ryan Roberts Cc: Stafford Horne Cc: Stefan Kristiansson Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Bogendoerfer Cc: Vasily Gorbik Cc: Vineet Gupta Cc: Vlastimil Babka Cc: WANG Xuerui Cc: Will Deacon Cc: Yoshinori Sato Cc: Zi Yan

mm: enable MMU_GATHER_RCU_TABLE_FREE for most 2-level architectures

2026-09-20T16:19:39+00:00

Commit e3ecf7c7d082 ("mm: pgtable: convert some architectures to use tlb_remove_ptdesc()") updated a number of architectures from using pagetable_dtor() + tlb_remove_page_ptdesc() to using tlb_remove_ptdesc() in __pte_free_tlb(). This is meaningful as tlb_remove_ptdesc() allows for RCU page table freeing if CONFIG_MMU_GATHER_RCU_TABLE_FREE is specified. The csky, hexagon, nios2, openrisc, sh (except X2) and m68k-sun3 architectures all have 2 levels of page tables, so the only page tables ever freed by mmu_gather are PTEs, so this update suffices to ensure that every page table freed by the mmu_gather mechanism is freed under RCU. Therefore, update all of these architectures to select CONFIG_MMU_GATHER_RCU_TABLE_FREE. This forms part of an overall effort to switch every architecture to this mode. Link: https://lore.kernel.org/20260911-rcu-pagetable-freeing-v3-2-7b8c86103821@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Signed-off-by: Andrew Morton Acked-by: Kiryl Shutsemau (Meta) Cc: Albert Ou Cc: Alexander Gordeev Cc: Alexandre Ghiti Cc: Andreas Larsson Cc: "Aneesh Kumar K.V" Cc: Anton Ivanov Cc: Arnd Bergmann Cc: Baolin Wang Cc: Barry Song Cc: "Borislav Petkov (AMD)" Cc: Catalin Marinas Cc: Christian Borntraeger Cc: Christian Zankel Cc: Dave Hansen Cc: David Hildenbrand Cc: David S. Miller Cc: Dev Jain Cc: Dinh Nguyen Cc: Geert Uytterhoeven Cc: Guo Ren Cc: Heiko Carstens Cc: Helge Deller Cc: "H. Peter Anvin" Cc: Huacai Chen Cc: Hugh Dickins Cc: Ingo Molnar Cc: James Bottomley Cc: Jason Gunthorpe Cc: Johannes Berg Cc: John Hubbard Cc: John Paul Adrian Glaubitz Cc: Jonas Bonn Cc: Lance Yang Cc: Liam R. Howlett Cc: Madhavan Srinivasan Cc: Magnus Lindholm Cc: Marc Rutland Cc: Matt Turner Cc: Max Filippov Cc: Michael Ellerman Cc: Michal Hocko Cc: Michal Simek Cc: Mike Rapoport Cc: Nicholas Piggin Cc: Palmer Dabbelt Cc: Peter Xu Cc: Peter Zijlstra Cc: Richard Henderson Cc: Richard Weinberger Cc: Rich Felker Cc: Russell King Cc: Ryan Roberts Cc: Stafford Horne Cc: Stefan Kristiansson Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Bogendoerfer Cc: Vasily Gorbik Cc: Vineet Gupta Cc: Vlastimil Babka Cc: WANG Xuerui Cc: Will Deacon Cc: Yoshinori Sato Cc: Zi Yan

m68k: Enable dead code elimination

2025-07-06T10:50:50+00:00

Allow the experimental dead code elimination config to be enabled. For my 68000 nommu config this frees up a few hundred K of memory so seems worth while. Boot and build tested on nommu and mmu enabled configs. Before: Memory: 5388K/8192K available (1986K kernel code, 114K rwdata, 244K rodata, 92K init, 41K bss, 2624K reserved, 0K cma-reserved) After Memory: 5684K/8192K available (1714K kernel code, 112K rwdata, 228K rodata, 92K init, 37K bss, 2328K reserved, 0K cma-reserved) Signed-off-by: Daniel Palmer Acked-by: Greg Ungerer Tested-by: Finn Thain Reviewed-by: Geert Uytterhoeven Link: https://lore.kernel.org/20250416114240.2929832-1-daniel@0x0f.com Signed-off-by: Geert Uytterhoeven

m68k: coldfire: select PCI_IOMAP for PCI

2025-03-24T14:41:07+00:00

After I dropped CONFIG_GENERIC_IOMAP, some PCI drivers started failing to link when CONFIG_MMU is disabled: ERROR: modpost: "pci_iounmap" [drivers/video/fbdev/i740fb.ko] undefined! ERROR: modpost: "pci_iounmap" [drivers/video/fbdev/vt8623fb.ko] undefined! ERROR: modpost: "pci_iomap_wc" [drivers/video/fbdev/vt8623fb.ko] undefined! ERROR: modpost: "pci_iomap" [drivers/video/fbdev/vt8623fb.ko] undefined! ERROR: modpost: "pci_iounmap" [drivers/video/fbdev/s3fb.ko] undefined! ... It turns out that there were two mistakes in my patch: on !MMU I forgot to enable CONFIG_GENERIC_PCI_IOMAP, and for Coldfire with MMU enabled, teh GENERIC_IOMAP was left in place but incorrectly configured. Fixes: 9d48cc07d0d7 ("m68k/nommu: stop using GENERIC_IOMAP") Reported-by: Greg Ungerer Acked-by: Greg Ungerer Signed-off-by: Arnd Bergmann

m68k/nommu: stop using GENERIC_IOMAP

2025-03-15T10:07:07+00:00

There is no need to go through the GENERIC_IOMAP wrapper for PIO on nommu platforms, since these always come from PCI I/O space that is itself memory mapped. Instead, the generic ioport_map() can just return the MMIO location of the ports directly by applying the PCI_IO_PA offset, while ioread32/iowrite32 trivially turn into readl/writel as they do on most other architectures. Signed-off-by: Arnd Bergmann

m68k: Use kernel's generic muldi3 libgcc function

2024-12-09T12:29:17+00:00

Use the kernels own generic lib/muldi3.c implementation of muldi3 for 68K machines. Some 68K CPUs support 64bit multiplies so move the arch specific umul_ppmm() macro into a header file that is included by lib/muldi3.c. That way it can take advantage of the single instruction when available. There does not appear to be any existing mechanism for the generic lib/muldi3.c code to pick up an external arch definition of umul_ppmm(). Create an arch specific libgcc.h that can optionally be included by the system include/linux/libgcc.h to allow for this. Somewhat oddly there is also a similar definition of umul_ppmm() in the non-architecture code in lib/crypto/mpi/longlong.h for a wide range or machines. Its presence ends up complicating the include setup and means not being able to use something like compiler.h instead. Actually there is a few other defines of umul_ppmm() macros spread around in various architectures, but not directly usable for the m68k case. Signed-off-by: Greg Ungerer Link: https://lore.kernel.org/20231113133209.1367286-1-gerg@linux-m68k.org Reviewed-by: Geert Uytterhoeven Reviewed-by: Arnd Bergmann Signed-off-by: Geert Uytterhoeven

m68k: Move Sun 3 into a top-level platform option

2024-11-06T14:10:14+00:00

It is possible to select an m68k MMU build but not actually enable any of the three MMU options, which then results in a build failure: arch/m68k/include/asm/page.h:10:25: error: 'CONFIG_PAGE_SHIFT' undeclared here (not in a function); did you mean 'CONFIG_LOG_BUF_SHIFT'? Change the Kconfig selection to ensure that exactly one of the three options is always enabled whenever an MMU-enabled kernel is built, but moving CONFIG_SUN3 into a top-level option next to M68KCLASSIC and COLDFIRE. All defconfig files should keep working without changes, but alldefconfig now builds support for the classic MMU. Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202408032138.P7sBvIns-lkp@intel.com/ Signed-off-by: Arnd Bergmann Acked-by: Greg Ungerer Reviewed-by: Geert Uytterhoeven Link: https://lore.kernel.org/20241030195638.22542-1-arnd@kernel.org Signed-off-by: Geert Uytterhoeven

m68k: Move ARCH_HAS_CPU_CACHE_ALIASING

2024-05-08T15:43:22+00:00

Move the recently added ARCH_HAS_CPU_CACHE_ALIASING to restore alphabetical sort order. Fixes: 8690bbcf3b7010b3 ("Introduce cpu_dcache_is_aliasing() across all architectures") Signed-off-by: Geert Uytterhoeven Reviewed-by: Mathieu Desnoyers Link: https://lore.kernel.org/r/4574ad6cc1117e4b5d29812c165bf7f6e5b60773.1714978406.git.geert@linux-m68k.org