linux-kernel - Re: [GIT PULL] device-dax for 5.1: PMEM as RAM

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Message-ID: <CAHk-=wjvmwD_0=CRQtNs5RBh8oJwrriXDn+XNWOU=wk8OyQ5ew@mail.gmail.com>
Date:   Sun, 10 Mar 2019 13:01:43 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux MM <linux-mm@...ck.org>,
        Dave Hansen <dave.hansen@...el.com>
Subject: Re: [GIT PULL] device-dax for 5.1: PMEM as RAM

On Sun, Mar 10, 2019 at 12:54 PM Dan Williams <dan.j.williams@...el.com> wrote:
>
> Hi Linus, please pull from:
>
>   git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm
> tags/devdax-for-5.1
>
> ...to receive new device-dax infrastructure to allow persistent memory
> and other "reserved" / performance differentiated memories, to be
> assigned to the core-mm as "System RAM".

I'm not pulling this until I get official Intel clarification on the
whole "pmem vs rep movs vs machine check" behavior.

Last I saw it was deadly and didn't work, and we have a whole "mc-safe
memory copy" thing for it in the kernel because repeat string
instructions didn't work correctly on nvmem.

No way am I exposing any users to something like that.

We need a way to know when it works and when it doesn't, and only do
it when it's safe.

                    Linus