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Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy()

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On Wed, Feb 17, 2016 at 10:20 AM, Tony Luck <tony.luck@intel.com> wrote:
>
> If we faulted during the copy, then 'trapnr' will say which type
> of trap (X86_TRAP_PF or X86_TRAP_MC) and 'remain' says how many
> bytes were not copied.

So apart from the naming, a couple of questions:

 - I'd like to see the actual *use* case explained, not just what it does.

 - why does this use the complex - and slower, on modern machines -
unrolled manual memory copy, when you might as well just use a single

     rep ; movsb

    which not only makes it smaller, but makes the exception fixup trivial.

 - why not make the "bytes remaining" the same as for a user-space
copy (ie return it as the return value)?

 - at that point, it ends up looking a *lot* like uaccess_try/catch,
which gets the error code from current_thread_info()->uaccess_err

Hmm?

          Linus

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[PATCH v11 0/4] Machine check recovery when kernel accesses poison Tony Luck <tony.luck@intel.com> - 2016-02-17 19:30 +0100
  [PATCH v11 4/4] x86: Create a new synthetic cpu capability for  machine check recovery Tony Luck <tony.luck@intel.com> - 2016-02-17 19:30 +0100
    [tip:x86/asm] x86/cpufeature:   Create a new synthetic cpu capability for machine check recovery tip-bot for Tony Luck <tipbot@zytor.com> - 2016-02-18 11:30 +0100
  [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() Tony Luck <tony.luck@intel.com> - 2016-02-17 19:30 +0100
    Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() Ingo Molnar <mingo@kernel.org> - 2016-02-18 09:30 +0100
      Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() Peter Zijlstra <peterz@infradead.org> - 2016-02-18 11:00 +0100
        Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() Borislav Petkov <bp@alien8.de> - 2016-02-18 11:30 +0100
        Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() Ingo Molnar <mingo@kernel.org> - 2016-02-18 11:30 +0100
          Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() Peter Zijlstra <peterz@infradead.org> - 2016-02-18 11:40 +0100
            RE: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() "Luck, Tony" <tony.luck@intel.com> - 2016-02-18 16:00 +0100
        Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() Ingo Molnar <mingo@kernel.org> - 2016-02-19 09:00 +0100
          Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() Peter Zijlstra <peterz@infradead.org> - 2016-02-19 09:50 +0100
            Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() Ingo Molnar <mingo@kernel.org> - 2016-02-19 11:00 +0100
      Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() Ingo Molnar <mingo@kernel.org> - 2016-02-18 11:40 +0100
        Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() Borislav Petkov <bp@alien8.de> - 2016-02-18 11:40 +0100
          Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() Ingo Molnar <mingo@kernel.org> - 2016-02-18 19:50 +0100
      Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() Borislav Petkov <bp@alien8.de> - 2016-02-18 11:40 +0100
      [PATCH v12] x86, mce: Add memcpy_trap() "Luck, Tony" <tony.luck@intel.com> - 2016-02-18 22:20 +0100
        Re: [PATCH v12] x86, mce: Add memcpy_trap() Ingo Molnar <mingo@kernel.org> - 2016-02-19 10:20 +0100
          Re: [PATCH v13] x86, mce: Add memcpy_trap() "Luck, Tony" <tony.luck@intel.com> - 2016-02-19 19:00 +0100
    Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() Linus Torvalds <torvalds@linux-foundation.org> - 2016-02-18 19:20 +0100
      Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() "Luck, Tony" <tony.luck@intel.com> - 2016-02-18 20:00 +0100
        Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() Ingo Molnar <mingo@kernel.org> - 2016-02-18 21:20 +0100
          Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() Dan Williams <dan.j.williams@intel.com> - 2016-02-18 22:40 +0100
      Re: [PATCH v11 3/4] x86, mce: Add __mcsafe_copy() Ingo Molnar <mingo@kernel.org> - 2016-02-18 20:00 +0100

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