Re: [PATCH v4 00/18] Tidy up cache.S

[Ard Biesheuvel <ardb@kernel.org>]

On Mon, 24 May 2021 at 10:30, Fuad Tabba <tabba@google.com> wrote:
>
> Hi,
>
> Changes since v3 [1]:
> - Rebased onto v5.13-rc3
> - Redid __flush_cache_range to use dcache_by_line_op (Mark)
> - Remove user_alt macro (Mark)
> - Tidying up some code, comments, and commit messages. (Mark)
>
> This should cover all the feedback from v2 [2].
>
> Changes since v2 [2]:
> - Brought in Mark's patches that add conditional cache fixups, only generating
>   an extable entry if a label is provided [3]. NOTE: The patches missed some of
>   the code comments to reflect the changes. I took the liberty of fixing the
>   comments in Mark's patch.
> - Tidied up the new cache flush (clean/invalidate) macro by removing code
>   duplication, conditional variables/labels. Moved the ttbr manipulation,
>   fixup handler, and rets inline in __flush_cache_user_range. (Mark)
> - Fixed comments and commit messages. (Mark)
>
> Changes since v1 [4]:
> - Apply ARM64_WORKAROUND_CLEAN_CACHE errata to
>   swsusp_arch_suspend_exit (Mark)
> - Remove toggling of uaccess from the newly created cache flush
>   (clean/invalidate) macro and leave it up to the caller (Robin)
> - Fix renaming of cache maintenance functions (Ard, Mark)
> - Fix comment on maintenance operations in machine_kexec_post_load (Ard)
> - Fix commit msg comments to clarify some of the changes and outline potential
>   performance impact (Mark)
> - Fix code comments that refer to flush_icache_range when the intended function
>   is __flush_icache_range
>
> As has been noted before [5], the code in cache.S isn't very tidy. Some of its
> functions accept address ranges by start and size, whereas others with similar
> names do so by start and end. This has resulted in at least one bug [6].
>
> Moreover, invalidate_icache_range and __flush_icache_range toggle uaccess,
> which isn't necessary because they work on kernel addresses [7].
>
> This patch series attempts to fix these issues, as well as tidy up the code in
> general to reduce ambiguity and make it consistent with Arm terminology and
> with the functions' actual operations.
>
> No functional change intended in this series. However, there might be a
> performance impact due to the reduced number of instructions in general.
>
> This series is based on v5.13-rc3. You can find the applied series here [8].
>
> Cheers,
> /fuad
>
> [1] https://lore.kernel.org/linux-arm-kernel/20210520124406.2731873-1-tabba@google.com/
> [2] https://lore.kernel.org/linux-arm-kernel/20210517075124.152151-1-tabba@google.com/
> [3] https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=arm64/cleanups/cache
> [4] https://lore.kernel.org/linux-arm-kernel/20210511144252.3779113-1-tabba@google.com/T/
> [5] https://lore.kernel.org/linux-arch/20200511075115.GA16134@willie-the-truck/
> [6] https://lore.kernel.org/linux-arch/20200510075510.987823-3-hch@lst.de/
> [7] https://lore.kernel.org/linux-arch/20200511110014.lb9PEahJ4hVOYrbwIb_qUHXyNy9KQzNFdb_I3YlzY6A@z/
> [8] https://android-kvm.googlesource.com/linux/+/refs/heads/tabba/fixcache-5.13
>
> Fuad Tabba (16):
>   arm64: Apply errata to swsusp_arch_suspend_exit
>   arm64: Do not enable uaccess for flush_icache_range
>   arm64: Do not enable uaccess for invalidate_icache_range
>   arm64: Downgrade flush_icache_range to invalidate
>   arm64: assembler: remove user_alt
>   arm64: Move documentation of dcache_by_line_op
>   arm64: Fix comments to refer to correct function __flush_icache_range
>   arm64: __inval_dcache_area to take end parameter instead of size
>   arm64: dcache_by_line_op to take end parameter instead of size
>   arm64: __flush_dcache_area to take end parameter instead of size
>   arm64: __clean_dcache_area_poc to take end parameter instead of size
>   arm64: __clean_dcache_area_pop to take end parameter instead of size
>   arm64: __clean_dcache_area_pou to take end parameter instead of size
>   arm64: sync_icache_aliases to take end parameter instead of size
>   arm64: Fix cache maintenance function comments
>   arm64: Rename arm64-internal cache maintenance functions
>
> Mark Rutland (2):
>   arm64: assembler: replace `kaddr` with `addr`
>   arm64: assembler: add conditional cache fixups
>

These all look good to me. Thanks for cleaning this up.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>

>  arch/arm64/include/asm/alternative-macros.h |   5 -
>  arch/arm64/include/asm/arch_gicv3.h         |   3 +-
>  arch/arm64/include/asm/assembler.h          |  80 ++++++----
>  arch/arm64/include/asm/cacheflush.h         |  71 +++++----
>  arch/arm64/include/asm/efi.h                |   2 +-
>  arch/arm64/include/asm/kvm_mmu.h            |   7 +-
>  arch/arm64/kernel/alternative.c             |   2 +-
>  arch/arm64/kernel/efi-entry.S               |   9 +-
>  arch/arm64/kernel/head.S                    |  13 +-
>  arch/arm64/kernel/hibernate-asm.S           |   7 +-
>  arch/arm64/kernel/hibernate.c               |  20 ++-
>  arch/arm64/kernel/idreg-override.c          |   3 +-
>  arch/arm64/kernel/image-vars.h              |   2 +-
>  arch/arm64/kernel/insn.c                    |   2 +-
>  arch/arm64/kernel/kaslr.c                   |  12 +-
>  arch/arm64/kernel/machine_kexec.c           |  30 ++--
>  arch/arm64/kernel/probes/uprobes.c          |   2 +-
>  arch/arm64/kernel/smp.c                     |   8 +-
>  arch/arm64/kernel/smp_spin_table.c          |   7 +-
>  arch/arm64/kernel/sys_compat.c              |   2 +-
>  arch/arm64/kvm/arm.c                        |   2 +-
>  arch/arm64/kvm/hyp/nvhe/cache.S             |   4 +-
>  arch/arm64/kvm/hyp/nvhe/setup.c             |   3 +-
>  arch/arm64/kvm/hyp/nvhe/tlb.c               |   2 +-
>  arch/arm64/kvm/hyp/pgtable.c                |  13 +-
>  arch/arm64/lib/uaccess_flushcache.c         |   4 +-
>  arch/arm64/mm/cache.S                       | 158 ++++++++++----------
>  arch/arm64/mm/flush.c                       |  29 ++--
>  28 files changed, 282 insertions(+), 220 deletions(-)
>
>
> base-commit: c4681547bcce777daf576925a966ffa824edd09d
> --
> 2.31.1.818.g46aad6cb9e-goog
>

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