[v3,0/2] Renovate memcpy_mcsafe with copy_mc_to_{user, kernel}
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Message ID 158992635164.403910.2616621400995359522.stgit@dwillia2-desk3.amr.corp.intel.com
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  • Renovate memcpy_mcsafe with copy_mc_to_{user, kernel}
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Dan Williams May 19, 2020, 10:12 p.m. UTC
Changes since v2 [1]:
- Replace the non-descriptive copy_safe() with copy_mc_to_user() and
  copy_mc_to_kernel() several code organization cleanups resulted from
  this rename, which further proves the point that the name deeply
  matters for maintainability in this case. (Linus)

- Do not use copy_user_generic() as the generic x86 backend for
  copy_mc_to_user() since the #MC handler explicitly wants the exception
  to be trapped by a _ASM_EXTABLE_FAULT handler. (Vivek).

- Rename copy_safe_slow() to copy_mc_fragile() to better indicate what
  the implementation is handling. copy_safe_fast() is replaced with
  copy_mc_generic().

---

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.

---

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_64.h                  |   35 ++--
 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/copy_safe_test.h        |   13 ++
 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 -
 .../testing/selftests/powerpc/copyloops/copy_mc.S  |    0 
 36 files changed, 460 insertions(+), 522 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
 create mode 100644 tools/arch/x86/include/asm/copy_safe_test.h
 delete mode 100644 tools/arch/x86/include/asm/mcsafe_test.h
 delete mode 100644 tools/perf/bench/mem-memcpy-x86-64-lib.c
 rename tools/testing/selftests/powerpc/copyloops/{memcpy_mcsafe_64.S => copy_mc.S} (100%)

base-commit: bba413deb1065f1291cb1f366247513f11215520