[RFC PATCH -next V3 0/6]arm64: add machine check safe support

[Tong Tiangen]

With the increase of memory capacity and density, the probability of
memory error increases. The increasing size and density of server RAM
in the data center and cloud have shown increased uncorrectable memory
errors.

Currently, the kernel has a mechanism to recover from hardware memory
errors. This patchset provides an new recovery mechanism.

For arm64, the hardware memory error handling is do_sea() which divided
into two cases:
 1. The user state consumed the memory errors, the solution is kill the
    user process and isolate the error page.
 2. The kernel state consumed the memory errors, the solution is panic.

For case 2, Undifferentiated panic maybe not the optimal choice, it can be
handled better, in some scenes, we can avoid panic, such as uaccess, if the
uaccess fails due to memory error, only the user process will be affected,
kill the user process and isolate the user page with hardware memory errors
is a better choice.

This patchset can be divided into three parts:
 1. Patch 0/1    - make some minor fixes to the associated code.
 2. Patch 3      - arm64 add support for machine check safe framework.
 3. Pathc 4/5/6  - arm64 add uaccess and cow to machine check safe.

Since V3:
 1. According to Mark's suggestion, all uaccess can be recovered due to
    memory error.
 2. Scenario pagecache reading is also supported as part of uaccess
    (copy_to_user()) and duplication code problem is also solved. 
    Thanks for Robin's suggestion.
 3. According Mark's suggestion, update commit message of patch 2/5.
 4. According Borisllav's suggestion, update commit message of patch 1/5.

Since V2:
 1.Consistent with PPC/x86, Using CONFIG_ARCH_HAS_COPY_MC instead of
   ARM64_UCE_KERNEL_RECOVERY.
 2.Add two new scenes, cow and pagecache reading.
 3.Fix two small bug(the first two patch).

V1 in here:
https://lore.kernel.org/lkml/20220323033705.3966643-1-tongtiangen@xxxxxxxxxx/

Tong Tiangen (6):
  x86: fix function define in copy_mc_to_user
  arm64: fix types in copy_highpage()
  arm64: add support for machine check error safe
  arm64: add copy_{to, from}_user to machine check safe
  arm64: add {get, put}_user to machine check safe
  arm64: add cow to machine check safe

 arch/arm64/Kconfig                   |  1 +
 arch/arm64/include/asm/asm-extable.h | 30 +++++++++
 arch/arm64/include/asm/asm-uaccess.h | 16 +++++
 arch/arm64/include/asm/extable.h     |  1 +
 arch/arm64/include/asm/page.h        | 10 +++
 arch/arm64/include/asm/uaccess.h     |  4 +-
 arch/arm64/lib/Makefile              |  2 +
 arch/arm64/lib/copy_from_user.S      | 15 +++--
 arch/arm64/lib/copy_page_mc.S        | 99 ++++++++++++++++++++++++++++
 arch/arm64/lib/copy_to_user.S        | 25 ++++---
 arch/arm64/mm/copypage.c             | 36 ++++++++--
 arch/arm64/mm/extable.c              | 22 +++++++
 arch/arm64/mm/fault.c                | 28 ++++++++
 arch/x86/include/asm/uaccess.h       |  1 +
 include/linux/highmem.h              |  8 +++
 include/linux/uaccess.h              |  8 +++
 mm/memory.c                          |  2 +-
 17 files changed, 286 insertions(+), 22 deletions(-)
 create mode 100644 arch/arm64/lib/copy_page_mc.S

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2.18.0.huawei.25