Re: [PATCH v2 16/17] x86/insn: remove pcommit
From: Dan Williams
Date: Fri Jul 22 2016 - 20:54:59 EST
On Fri, Jul 22, 2016 at 9:52 AM, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
> * Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
>> On Tue, Jul 12, 2016 at 3:12 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
>> > On Tue, Jul 12, 2016 at 7:57 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> 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." 
>> > 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.
>> > : 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.
> Since it's just a removal AFAICS that the rest of your series should not depend
> on, can you submit it to the x86 tree?
This patch depends on the previous patches in the series removing
calls to pcommit_sfence().