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

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Message-ID: <20160723074906.GA21154@gmail.com>
Date:	Sat, 23 Jul 2016 09:49:06 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-nvdimm <linux-nvdimm@...1.01.org>,
	Xiao Guangrong <guangrong.xiao@...ux.intel.com>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Linux ACPI <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Christoph Hellwig <hch@....de>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>,
	Andy Lutomirski <luto@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...e.de>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>
Subject: Re: [PATCH v2 16/17] x86/insn: remove pcommit


* Dan Williams <dan.j.williams@...el.com> wrote:

> On Fri, Jul 22, 2016 at 9:52 AM, Ingo Molnar <mingo@...nel.org> wrote:
> >
> > * Dan Williams <dan.j.williams@...el.com> wrote:
> >
> >> On Tue, Jul 12, 2016 at 3:12 PM, Dan Williams <dan.j.williams@...el.com> wrote:
> >> > On Tue, Jul 12, 2016 at 7:57 AM, Peter Zijlstra <peterz@...radead.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.
> >
> > 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().

Ok, and the patch looks harmless:

Acked-by: Ingo Molnar <mingo@...nel.org>

Thanks,

	Ingo