Re: [PATCH v8 00/20] Convert x86 & arm64 to use generic page walk

Steven Price
2019-04-10T14:56:47Z

Hi all,

Gentle ping: who can take this? Is there anything blocking this series?

Thanks,

Steve

On 03/04/2019 15:16, Steven Price wrote:
> Most architectures current have a debugfs file for dumping the kernel
> page tables. Currently each architecture has to implement custom
> functions for walking the page tables because the generic
> walk_page_range() function is unable to walk the page tables used by the
> kernel.
>
> This series extends the capabilities of walk_page_range() so that it can
> deal with the page tables of the kernel (which have no VMAs and can
> contain larger huge pages than exist for user space). x86 and arm64 are
> then converted to make use of walk_page_range() removing the custom page
> table walkers.
>
> To enable a generic page table walker to walk the unusual mappings of
> the kernel we need to implement a set of functions which let us know
> when the walker has reached the leaf entry. Since arm, powerpc, s390,
> sparc and x86 all have p?d_large macros lets standardise on that and
> implement those that are missing.
>
> Potentially future changes could unify the implementations of the
> debugfs walkers further, moving the common functionality into common
> code. This would require a common way of handling the effective
> permissions (currently implemented only for x86) along with a per-arch
> way of formatting the page table information for debugfs. One
> immediate benefit would be getting the KASAN speed up optimisation in
> arm64 (and other arches) which is currently only implemented for x86.
>
> Also available as a git tree:
> git://linux-arm.org/linux-sp.git walk_page_range/v8
>
> Changes since v7:
> https://lore.kernel.org/lkml/20190328152104.23106-1-steven.price@arm.com/T/
> * Updated commit message in patch 2 to clarify that we rely on the page
> tables being walked to be the same page size/depth as the kernel's
> (since this confused me earlier today).
>
> Changes since v6:
> https://lore.kernel.org/lkml/20190326162624.20736-1-steven.price@arm.com/T/
> * Split the changes for powerpc. pmd_large() is now added in patch 4
> patch, and pmd_is_leaf() removed in patch 5.
>
> Changes since v5:
> https://lore.kernel.org/lkml/20190321141953.31960-1-steven.price@arm.com/T/
> * Updated comment for struct mm_walk based on Mike Rapoport's
> suggestion
>
> Changes since v4:
> https://lore.kernel.org/lkml/20190306155031.4291-1-steven.price@arm.com/T/
> * Correctly force result to a boolean in p?d_large for powerpc.
> * Added Acked-bys
> * Rebased onto v5.1-rc1
>
> Changes since v3:
> https://lore.kernel.org/lkml/20190227170608.27963-1-steven.price@arm.com/T/
> * Restored the generic macros, only implement p?d_large() for
> architectures that have support for large pages. This also means
> adding dummy #defines for architectures that define p?d_large as
> static inline to avoid picking up the generic macro.
> * Drop the 'depth' argument from pte_hole
> * Because we no longer have the depth for holes, we also drop support
> in x86 for showing missing pages in debugfs. See discussion below:
> https://lore.kernel.org/lkml/26df02dd-c54e-ea91-bdd1-0a4aad3a30ac@arm.com/
> * mips: only define p?d_large when _PAGE_HUGE is defined.
>
> Changes since v2:
> https://lore.kernel.org/lkml/20190221113502.54153-1-steven.price@arm.com/T/
> * Rather than attemping to provide generic macros, actually implement
> p?d_large() for each architecture.
>
> Changes since v1:
> https://lore.kernel.org/lkml/20190215170235.23360-1-steven.price@arm.com/T/
> * Added p4d_large() macro
> * Comments to explain p?d_large() macro semantics
> * Expanded comment for pte_hole() callback to explain mapping between
> depth and P?D
> * Handle folded page tables at all levels, so depth from pte_hole()
> ignores folding at any level (see real_depth() function in
> mm/pagewalk.c)
>
> Steven Price (20):
> arc: mm: Add p?d_large() definitions
> arm64: mm: Add p?d_large() definitions
> mips: mm: Add p?d_large() definitions
> powerpc: mm: Add p?d_large() definitions
> KVM: PPC: Book3S HV: Remove pmd_is_leaf()
> riscv: mm: Add p?d_large() definitions
> s390: mm: Add p?d_large() definitions
> sparc: mm: Add p?d_large() definitions
> x86: mm: Add p?d_large() definitions
> mm: Add generic p?d_large() macros
> mm: pagewalk: Add p4d_entry() and pgd_entry()
> mm: pagewalk: Allow walking without vma
> mm: pagewalk: Add test_p?d callbacks
> arm64: mm: Convert mm/dump.c to use walk_page_range()
> x86: mm: Don't display pages which aren't present in debugfs
> x86: mm: Point to struct seq_file from struct pg_state
> x86: mm+efi: Convert ptdump_walk_pgd_level() to take a mm_struct
> x86: mm: Convert ptdump_walk_pgd_level_debugfs() to take an mm_struct
> x86: mm: Convert ptdump_walk_pgd_level_core() to take an mm_struct
> x86: mm: Convert dump_pagetables to use walk_page_range
>
> arch/arc/include/asm/pgtable.h | 1 +
> arch/arm64/include/asm/pgtable.h | 2 +
> arch/arm64/mm/dump.c | 117 +++----
> arch/mips/include/asm/pgtable-64.h | 8 +
> arch/powerpc/include/asm/book3s/64/pgtable.h | 30 +-
> arch/powerpc/kvm/book3s_64_mmu_radix.c | 12 +-
> arch/riscv/include/asm/pgtable-64.h | 7 +
> arch/riscv/include/asm/pgtable.h | 7 +
> arch/s390/include/asm/pgtable.h | 2 +
> arch/sparc/include/asm/pgtable_64.h | 2 +
> arch/x86/include/asm/pgtable.h | 10 +-
> arch/x86/mm/debug_pagetables.c | 8 +-
> arch/x86/mm/dump_pagetables.c | 347 ++++++++++---------
> arch/x86/platform/efi/efi_32.c | 2 +-
> arch/x86/platform/efi/efi_64.c | 4 +-
> include/asm-generic/pgtable.h | 19 +
> include/linux/mm.h | 26 +-
> mm/pagewalk.c | 76 +++-
> 18 files changed, 407 insertions(+), 273 deletions(-)
>