Re: [PATCH v2 16/17] x86/insn: remove pcommit

From	Dan Williams <dan.j.williams@intel.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2 16/17] x86/insn: remove pcommit
Date	2016-07-22 18:00 +0200
Message-ID	<rXL1M-7Ib-23@gated-at.bofh.it> (permalink)
References	<rTdBn-3ye-3@gated-at.bofh.it> <rTdBn-3ye-1@gated-at.bofh.it> <rU7ke-6jl-17@gated-at.bofh.it> <rUec2-2Bd-25@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Tue, Jul 12, 2016 at 3:12 PM, Dan Williams <dan.j.williams@intel.com> wrote:
> On Tue, Jul 12, 2016 at 7:57 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>> On Sat, Jul 09, 2016 at 08:25:54PM -0700, Dan Williams wrote:
>>> The pcommit instruction is being deprecated in favor of either ADR
>>> (asynchronous DRAM refresh: flush-on-power-fail) at the platform level, or
>>> posted-write-queue flush addresses as defined by the ACPI 6.x NFIT (NVDIMM
>>> Firmware Interface Table).
>>
>>>  arch/x86/include/asm/cpufeatures.h                 |    1
>>>  arch/x86/include/asm/special_insns.h               |   46 --------------------
>>>  arch/x86/lib/x86-opcode-map.txt                    |    2 -
>>>  tools/objtool/arch/x86/insn/x86-opcode-map.txt     |    2 -
>>>  tools/perf/arch/x86/tests/insn-x86-dat-32.c        |    2 -
>>>  tools/perf/arch/x86/tests/insn-x86-dat-64.c        |    2 -
>>>  tools/perf/arch/x86/tests/insn-x86-dat-src.c       |    4 --
>>
>> Just deprecated, or is it completely eradicated, removed from history,
>> will never ever happen and we'll reissue the opcode for something else?
>>
>> Because if its only deprecated then removing it from the instruction
>> decoders seems wrong, old binaries might still contain the opcode.
>
> Eradicated.
>
> "The new instructions like CLWB and CLFLUSHOPT will be rolled into the
> SDM but PCOMMIT will be removed from the Extensions doc and not rolled
> into the SDM." [1]
>
> Existing binaries are already gating their usage on the presence of
> the cpu id flag, that flag and the instruction opcode are reserved
> going forward.
>
> [1]: https://lists.01.org/pipermail/linux-nvdimm/2016-June/005923.html

x86 maintainers, I have the other patches in this series queued in
-next. Please ack this one and I'll add it for v4.8-rc1, or otherwise
let me know how you want to handle this patch.

Thread

[PATCH v2 16/17] x86/insn: remove pcommit Dan Williams <dan.j.williams@intel.com> - 2016-07-10 05:30 +0200
  Re: [PATCH v2 16/17] x86/insn: remove pcommit Peter Zijlstra <peterz@infradead.org> - 2016-07-12 17:00 +0200
    Re: [PATCH v2 16/17] x86/insn: remove pcommit Dan Williams <dan.j.williams@intel.com> - 2016-07-13 00:20 +0200
      Re: [PATCH v2 16/17] x86/insn: remove pcommit Dan Williams <dan.j.williams@intel.com> - 2016-07-22 18:00 +0200
        Re: [PATCH v2 16/17] x86/insn: remove pcommit Ingo Molnar <mingo@kernel.org> - 2016-07-22 19:00 +0200
          Re: [PATCH v2 16/17] x86/insn: remove pcommit Dan Williams <dan.j.williams@intel.com> - 2016-07-23 03:00 +0200
            Re: [PATCH v2 16/17] x86/insn: remove pcommit Ingo Molnar <mingo@kernel.org> - 2016-07-23 09:50 +0200

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