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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 2016-07-13 00:20 +0200
Message-ID <rUec2-2Bd-25@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>
Organization linux.* mail to news gateway

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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

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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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