Re: [PATCH v5 0/2] Renovate memcpy_mcsafe with copy_mc_to_{user, kernel}

[Dan Williams]

On Wed, May 27, 2020 at 4:32 PM Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
>
> Changes since v4 [1]:
> - Fix up .gitignore for PowerPC test artifacts (Michael)
>
> - Collect Michael's Ack.
>
> [1]: http://lore.kernel.org/r/159010126119.975921.6614194205409771984.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> ---
>
> The primary motivation to go touch memcpy_mcsafe() is that the existing
> benefit of doing slow "handle with care" copies is obviated on newer
> CPUs. With that concern lifted it also obviates the need to continue to
> update the MCA-recovery capability detection code currently gated by
> "mcsafe_key". Now the old "mcsafe_key" opt-in to perform the copy with
> concerns for recovery fragility can instead be made an opt-out from the
> default fast copy implementation (enable_copy_mc_fragile()).
>
> The discussion with Linus on the first iteration of this patch
> identified that memcpy_mcsafe() was misnamed relative to its usage. The
> new names copy_mc_to_user() and copy_mc_to_kernel() clearly indicate the
> intended use case and lets the architecture organize the implementation
> accordingly.
>
> For both powerpc and x86 a copy_mc_generic() implementation is added as
> the backend for these interfaces.
>
> Patches are relative to tip/master.

I have not heard any additional feedback, or seen tip-bot traffic. Is
this still under consideration for v5.8? The kernel's behavior on new
platforms regresses without this, recoverable #MC escalates to panic.


>
> ---
>
> Dan Williams (2):
>       x86, powerpc: Rename memcpy_mcsafe() to copy_mc_to_{user,kernel}()
>       x86/copy_mc: Introduce copy_mc_generic()
>
>
>  arch/powerpc/Kconfig                               |    2
>  arch/powerpc/include/asm/string.h                  |    2
>  arch/powerpc/include/asm/uaccess.h                 |   40 +++--
>  arch/powerpc/lib/Makefile                          |    2
>  arch/powerpc/lib/copy_mc_64.S                      |    4
>  arch/x86/Kconfig                                   |    2
>  arch/x86/Kconfig.debug                             |    2
>  arch/x86/include/asm/copy_mc_test.h                |   75 +++++++++
>  arch/x86/include/asm/mcsafe_test.h                 |   75 ---------
>  arch/x86/include/asm/string_64.h                   |   32 ----
>  arch/x86/include/asm/uaccess.h                     |   21 +++
>  arch/x86/include/asm/uaccess_64.h                  |   20 --
>  arch/x86/kernel/cpu/mce/core.c                     |    8 -
>  arch/x86/kernel/quirks.c                           |    9 -
>  arch/x86/lib/Makefile                              |    1
>  arch/x86/lib/copy_mc.c                             |   64 ++++++++
>  arch/x86/lib/copy_mc_64.S                          |  165 ++++++++++++++++++++
>  arch/x86/lib/memcpy_64.S                           |  115 --------------
>  arch/x86/lib/usercopy_64.c                         |   21 ---
>  drivers/md/dm-writecache.c                         |   15 +-
>  drivers/nvdimm/claim.c                             |    2
>  drivers/nvdimm/pmem.c                              |    6 -
>  include/linux/string.h                             |    9 -
>  include/linux/uaccess.h                            |    9 +
>  include/linux/uio.h                                |   10 +
>  lib/Kconfig                                        |    7 +
>  lib/iov_iter.c                                     |   43 +++--
>  tools/arch/x86/include/asm/mcsafe_test.h           |   13 --
>  tools/arch/x86/lib/memcpy_64.S                     |  115 --------------
>  tools/objtool/check.c                              |    5 -
>  tools/perf/bench/Build                             |    1
>  tools/perf/bench/mem-memcpy-x86-64-lib.c           |   24 ---
>  tools/testing/nvdimm/test/nfit.c                   |   48 +++---
>  .../testing/selftests/powerpc/copyloops/.gitignore |    2
>  tools/testing/selftests/powerpc/copyloops/Makefile |    6 -
>  .../selftests/powerpc/copyloops/copy_mc_64.S       |    1
>  .../selftests/powerpc/copyloops/memcpy_mcsafe_64.S |    1
>  37 files changed, 451 insertions(+), 526 deletions(-)
>  rename arch/powerpc/lib/{memcpy_mcsafe_64.S => copy_mc_64.S} (98%)
>  create mode 100644 arch/x86/include/asm/copy_mc_test.h
>  delete mode 100644 arch/x86/include/asm/mcsafe_test.h
>  create mode 100644 arch/x86/lib/copy_mc.c
>  create mode 100644 arch/x86/lib/copy_mc_64.S
>  delete mode 100644 tools/arch/x86/include/asm/mcsafe_test.h
>  delete mode 100644 tools/perf/bench/mem-memcpy-x86-64-lib.c
>  create mode 120000 tools/testing/selftests/powerpc/copyloops/copy_mc_64.S
>  delete mode 120000 tools/testing/selftests/powerpc/copyloops/memcpy_mcsafe_64.S
>
> base-commit: 229aaa8c059f2c908e0561453509f996f2b2d5c4