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[209.85.208.181]) by smtp.gmail.com with ESMTPSA id z4sm1124622ljz.43.2019.03.11.17.07.59 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 11 Mar 2019 17:07:59 -0700 (PDT) Received: by mail-lj1-f181.google.com with SMTP id v10so703629lji.3 for ; Mon, 11 Mar 2019 17:07:59 -0700 (PDT) X-Received: by 2002:a2e:8018:: with SMTP id j24mr17374435ljg.118.1552349279030; Mon, 11 Mar 2019 17:07:59 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Linus Torvalds Date: Mon, 11 Mar 2019 17:07:43 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [GIT PULL] device-dax for 5.1: PMEM as RAM To: Dan Williams Cc: Linux Kernel Mailing List , linux-nvdimm , Linux MM , Dave Hansen , "Luck, Tony" Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Mar 11, 2019 at 8:37 AM Dan Williams wrote: > > Another feature the userspace tooling can support for the PMEM as RAM > case is the ability to complete an Address Range Scrub of the range > before it is added to the core-mm. I.e at least ensure that previously > encountered poison is eliminated. Ok, so this at least makes sense as an argument to me. In the "PMEM as filesystem" part, the errors have long-term history, while in "PMEM as RAM" the memory may be physically the same thing, but it doesn't have the history and as such may not be prone to long-term errors the same way. So that validly argues that yes, when used as RAM, the likelihood for errors is much lower because they don't accumulate the same way. > The driver can also publish an > attribute to indicate when rep; mov is recoverable, and gate the > hotplug policy on the result. In my opinion a positive indicator of > the cpu's ability to recover rep; mov exceptions is a gap that needs > addressing. Is there some way to say "don't raise MC for this region"? Or at least limit it to a nonfatal one? Linus