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SubjectRe: [RFC V1 00/31] mm/mmap: Drop protection_map[] and platform's __SXXX/__PXXX requirements
Hi Anshuman,

On Mon, Jan 24, 2022 at 06:26:37PM +0530, Anshuman Khandual wrote:
> protection_map[] is an array based construct that translates given vm_flags
> combination. This array contains page protection map, which is populated by
> the platform via [__S000 .. __S111] and [__P000 .. __P111] exported macros.
> Primary usage for protection_map[] is for vm_get_page_prot(), which is used
> to determine page protection value for a given vm_flags. vm_get_page_prot()
> implementation, could again call platform overrides arch_vm_get_page_prot()
> and arch_filter_pgprot(). Some platforms override protection_map[] that was
> originally built with __SXXX/__PXXX with different runtime values.
>
> Currently there are multiple layers of abstraction i.e __SXXX/__PXXX macros
> , protection_map[], arch_vm_get_page_prot() and arch_filter_pgprot() built
> between the platform and generic MM, finally defining vm_get_page_prot().
>
> Hence this series proposes to drop all these abstraction levels and instead
> just move the responsibility of defining vm_get_page_prot() to the platform
> itself making it clean and simple.
>
> This first introduces ARCH_HAS_VM_GET_PAGE_PROT which enables the platforms
> to define custom vm_get_page_prot(). This starts converting platforms that
> either change protection_map[] or define the overrides arch_filter_pgprot()
> or arch_vm_get_page_prot() which enables for those constructs to be dropped
> off completely. This series then converts remaining platforms which enables
> for __SXXX/__PXXX constructs to be dropped off completely. Finally it drops
> the generic vm_get_page_prot() and then ARCH_HAS_VM_GET_PAGE_PROT as every
> platform now defines their own vm_get_page_prot().

I generally like the idea, I just think the conversion can be more straight
forward. Rather than adding ARCH_HAS_VM_GET_PAGE_PROT and then dropping it,
why won't me make the generic vm_get_page_prot() __weak, then add per-arch
implementation and in the end drop the generic one?

> The last patch demonstrates how vm_flags combination indices can be defined
> as macros and be replaces across all platforms (if required, not done yet).
>
> The series has been inspired from an earlier discuss with Christoph Hellwig
>
> https://lore.kernel.org/all/1632712920-8171-1-git-send-email-anshuman.khandual@arm.com/
>
> This series applies on 5.17-rc1 after the following patch.
>
> https://lore.kernel.org/all/1643004823-16441-1-git-send-email-anshuman.khandual@arm.com/
>
> This has been cross built for multiple platforms. I would like to get some
> early feed back on this proposal. All reviews and suggestions welcome.
>
> Hello Christoph,
>
> I have taken the liberty to preserve your authorship on the x86 patch which
> is borrowed almost as is from our earlier discussion. I have also added you
> as 'Suggested-by:' on the patch that adds config ARCH_HAS_VM_GET_PAGE_PROT.
> Nonetheless please feel free to correct me for any other missing authorship
> attributes I should have added. Thank you.
>
> - Anshuman
>
> Cc: Christoph Hellwig <hch@infradead.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
>
> Anshuman Khandual (30):
> mm/debug_vm_pgtable: Directly use vm_get_page_prot()
> mm/mmap: Clarify protection_map[] indices
> mm/mmap: Add new config ARCH_HAS_VM_GET_PAGE_PROT
> powerpc/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> arm64/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> sparc/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> mips/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> m68k/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> arm/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> mm/mmap: Drop protection_map[]
> mm/mmap: Drop arch_filter_pgprot()
> mm/mmap: Drop arch_vm_get_page_pgprot()
> s390/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> riscv/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> alpha/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> sh/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> arc/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> csky/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> extensa/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> parisc/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> openrisc/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> um/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> microblaze/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> nios2/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> hexagon/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> nds32/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> ia64/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
> mm/mmap: Drop generic vm_get_page_prot()
> mm/mmap: Drop ARCH_HAS_VM_GET_PAGE_PROT
> mm/mmap: Define macros for vm_flags access permission combinations
>
> Christoph Hellwig (1):
> x86/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
>
> arch/alpha/include/asm/pgtable.h | 17 -----
> arch/alpha/mm/init.c | 41 +++++++++++
> arch/arc/include/asm/pgtable-bits-arcv2.h | 17 -----
> arch/arc/mm/mmap.c | 41 +++++++++++
> arch/arm/include/asm/pgtable.h | 18 -----
> arch/arm/mm/mmu.c | 50 +++++++++++--
> arch/arm64/Kconfig | 1 -
> arch/arm64/include/asm/mman.h | 3 +-
> arch/arm64/include/asm/pgtable-prot.h | 18 -----
> arch/arm64/include/asm/pgtable.h | 2 +-
> arch/arm64/mm/mmap.c | 50 +++++++++++++
> arch/csky/include/asm/pgtable.h | 18 -----
> arch/csky/mm/init.c | 41 +++++++++++
> arch/hexagon/include/asm/pgtable.h | 24 -------
> arch/hexagon/mm/init.c | 42 +++++++++++
> arch/ia64/include/asm/pgtable.h | 17 -----
> arch/ia64/mm/init.c | 43 ++++++++++-
> arch/m68k/include/asm/mcf_pgtable.h | 59 ---------------
> arch/m68k/include/asm/motorola_pgtable.h | 22 ------
> arch/m68k/include/asm/sun3_pgtable.h | 22 ------
> arch/m68k/mm/init.c | 87 +++++++++++++++++++++++
> arch/m68k/mm/motorola.c | 44 +++++++++++-
> arch/microblaze/include/asm/pgtable.h | 17 -----
> arch/microblaze/mm/init.c | 41 +++++++++++
> arch/mips/include/asm/pgtable.h | 22 ------
> arch/mips/mm/cache.c | 65 ++++++++++-------
> arch/nds32/include/asm/pgtable.h | 17 -----
> arch/nds32/mm/mmap.c | 41 +++++++++++
> arch/nios2/include/asm/pgtable.h | 16 -----
> arch/nios2/mm/init.c | 41 +++++++++++
> arch/openrisc/include/asm/pgtable.h | 18 -----
> arch/openrisc/mm/init.c | 41 +++++++++++
> arch/parisc/include/asm/pgtable.h | 20 ------
> arch/parisc/mm/init.c | 41 +++++++++++
> arch/powerpc/include/asm/mman.h | 3 +-
> arch/powerpc/include/asm/pgtable.h | 19 -----
> arch/powerpc/mm/mmap.c | 47 ++++++++++++
> arch/riscv/include/asm/pgtable.h | 16 -----
> arch/riscv/mm/init.c | 41 +++++++++++
> arch/s390/include/asm/pgtable.h | 17 -----
> arch/s390/mm/mmap.c | 41 +++++++++++
> arch/sh/include/asm/pgtable.h | 17 -----
> arch/sh/mm/mmap.c | 43 +++++++++++
> arch/sparc/include/asm/mman.h | 1 -
> arch/sparc/include/asm/pgtable_32.h | 19 -----
> arch/sparc/include/asm/pgtable_64.h | 19 -----
> arch/sparc/mm/init_32.c | 41 +++++++++++
> arch/sparc/mm/init_64.c | 71 +++++++++++++-----
> arch/um/include/asm/pgtable.h | 17 -----
> arch/um/kernel/mem.c | 41 +++++++++++
> arch/x86/Kconfig | 1 -
> arch/x86/include/asm/pgtable.h | 5 --
> arch/x86/include/asm/pgtable_types.h | 19 -----
> arch/x86/include/uapi/asm/mman.h | 14 ----
> arch/x86/mm/Makefile | 2 +-
> arch/x86/mm/mem_encrypt_amd.c | 4 --
> arch/x86/mm/pgprot.c | 71 ++++++++++++++++++
> arch/xtensa/include/asm/pgtable.h | 18 -----
> arch/xtensa/mm/init.c | 41 +++++++++++
> include/linux/mm.h | 45 ++++++++++--
> include/linux/mman.h | 4 --
> mm/Kconfig | 3 -
> mm/debug_vm_pgtable.c | 27 +++----
> mm/mmap.c | 22 ------
> 64 files changed, 1150 insertions(+), 636 deletions(-)
> create mode 100644 arch/x86/mm/pgprot.c
>
> --
> 2.25.1
>
>

--
Sincerely yours,
Mike.

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