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[209.85.220.65]) by mx.google.com with SMTPS id e68sor1806564oih.92.2019.03.10.16.54.41 for (Google Transport Security); Sun, 10 Mar 2019 16:54:42 -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=lMsDbSqu; 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=yoSe6Z/a+RRQ6U0Ns6hRLVWf24WoPrnlmUg/LWRdcts=; b=lMsDbSquzK+wxeInWsUe1ndqpM9OM9/OB7dMQrMvZ9097++6Ct+wpXm0dqgb7ZjMyL mnqx0XfIpkzoj3r/+wUm5jvJX0lYV3hfaJd0jcSPb/keDEt4peF0a8NgAbV3h10yVcgy faZdoQg4zPIIaqHJQ7v3Vovrjqd2qjwZ2ipGKqFU1ljVegDQ4Z2ncr9m/1TiR1iCaFM4 pMLwGTJI8ZEw/OgebS+k25P3TqVXeRLU4xX8OL7LKxMR/HWuJCu/ce/MOS1+ajJ+f4cf HaYNH/45TwyQGagvuLDV8rT4jbb2uUs7OpsJs/8eXeAAJvkFg0IZ55sa2HhDLJiHcOHa YDVw== X-Google-Smtp-Source: APXvYqwFn91XEpww+BFQB83/xV8SzljK9yYHpQHlAWoikQE2Le/KJgxWPDHFRksbZv/CbhUUridG+auz58mLWbvTxrI= X-Received: by 2002:aca:fc06:: with SMTP id a6mr15527931oii.0.1552262081496; Sun, 10 Mar 2019 16:54:41 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Dan Williams Date: Sun, 10 Mar 2019 16:54:29 -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: [ add Tony, who has wrestled with how to detect rep; movs recover-ability ] On Sun, Mar 10, 2019 at 1:02 PM Linus Torvalds wrote: > > On Sun, Mar 10, 2019 at 12:54 PM Dan Williams 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. Unfortunately this particular b0rkage is not constrained to nvmem. I.e. there's nothing specific about nvmem requiring mc-safe memory copy, it's a cpu problem consuming any poison regardless of source-media-type with "rep; movs".