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[209.85.220.65]) by mx.google.com with SMTPS id o6sor3703620oig.18.2019.03.11.17.30.13 for (Google Transport Security); Mon, 11 Mar 2019 17:30:13 -0700 (PDT) Received-SPF: pass (google.com: domain of dan.j.williams@intel.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@intel-com.20150623.gappssmtp.com header.s=20150623 header.b="tjGdxu/b"; spf=pass (google.com: domain of dan.j.williams@intel.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=dan.j.williams@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=96Eychx0pVXg5tC/lmw3nK92/kMpZpAcq39GwifwZoI=; b=tjGdxu/bVPVh9Ua5UQ8YtA22eqApz6aIzFPfYx/7CDlBMSMlZHU0eHNZdkYmi1qjsS OmHTQI2f2eb5YiKYmgKeN4CALQM8TaBXKfhHPZtA8LlA+Wl4IaWsIyyoHe4RKeXN7JyK 2oqiCUcYuzjD19Oz1vcxDOEwP0keO3Js0AntCZkGr7o3wJubBd7j754AQ+BahUJ7weyW VnQqxBLf8Pc9NU6+/3PfC/AMuqlQ4wQ3rdM2pF8OGCN3nhQ1++j3cDp98NsucCoxQeyc omm/sgZP15MkyeSNXf1CWIYFvXT//dFW7uamAA9EMQFBEQuF8Kiv3pSRBCXxmG/SLHfO FDOg== X-Google-Smtp-Source: APXvYqwlMK4Ji22rFS+MBGh9COVQcs3fw5qaMUPzkLdofXvv/AYErEbzrXXcIHwPq5L/VyLOpy4O8NJyIgC70phvAJ0= X-Received: by 2002:aca:3906:: with SMTP id g6mr10168oia.149.1552350611637; Mon, 11 Mar 2019 17:30:11 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Dan Williams Date: Mon, 11 Mar 2019 17:30:00 -0700 Message-ID: Subject: Re: [GIT PULL] device-dax for 5.1: PMEM as RAM To: Linus Torvalds 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 5:08 PM Linus Torvalds wrote: > > 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? I wish, but no. The poison consumption always raises the MC then it's whether MCI_STATUS_PCC (processor context corrupt) is set as to whether the cpu indicates it is safe to proceed. There's no way to indicate, "never set MCI_STATUS_PCC", or silence the exception.