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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id bd12si6070397plb.193.2019.02.06.12.49.58 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 06 Feb 2019 12:49:58 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=kjMhfcP6; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=NL1MPyRU/T/2aVS0UzGM98TCSfb5ympBh3xbI7SJ34A=; b=kjMhfcP6/nCSoSlWl2K7h4tCU K2r5F+WrqeCQDKBF4VVmFZdO5boPVHwGwaWTO2Bqp+nKvEdq+ZNoBMPuAPs3rrnRSHvcydo8c60Ee Zc9rJaOiEUGEz4+y+qKlnkVU2rVOeswtzmffDldixXaGdoqxclVsWsSKObzWa5v01UXR3hxh0LUjc lCjORh510SMfx5CEDfyN7x2k73Ylio2FCe9iICPDP/kCOxygcV2Ds0wGEiqOZqKtEGrfgeZhRn9Fi s5wTUFJfgRKHPyRNWHeQS55tsIsDEtFBuKPFb6OSatbKMpWxK+FAv7MO95tcPWJ6Wmc/1xKhMsHgH qv1E47GOQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1grU8o-0001SI-TO; Wed, 06 Feb 2019 20:49:54 +0000 Date: Wed, 6 Feb 2019 12:49:54 -0800 From: Matthew Wilcox To: Doug Ledford Cc: Christopher Lameter , Jason Gunthorpe , Jan Kara , Ira Weiny , lsf-pc@lists.linux-foundation.org, linux-rdma@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, John Hubbard , Jerome Glisse , Dan Williams , Dave Chinner , Michal Hocko Subject: Re: [LSF/MM TOPIC] Discuss least bad options for resolving longterm-GUP usage by RDMA Message-ID: <20190206204954.GS21860@bombadil.infradead.org> References: <20190206173114.GB12227@ziepe.ca> <20190206175233.GN21860@bombadil.infradead.org> <47820c4d696aee41225854071ec73373a273fd4a.camel@redhat.com> <01000168c43d594c-7979fcf8-b9c1-4bda-b29a-500efe001d66-000000@email.amazonses.com> <20190206194055.GP21860@bombadil.infradead.org> <20190206202021.GQ21860@bombadil.infradead.org> <20190206204128.GR21860@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.2 (2017-12-15) 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 Wed, Feb 06, 2019 at 03:47:53PM -0500, Doug Ledford wrote: > On Wed, 2019-02-06 at 12:41 -0800, Matthew Wilcox wrote: > > On Wed, Feb 06, 2019 at 03:28:35PM -0500, Doug Ledford wrote: > > > On Wed, 2019-02-06 at 12:20 -0800, Matthew Wilcox wrote: > > > > Not hot-unplugging the RDMA device but hot-unplugging an NV-DIMM. ^^^ I think you missed this line ^^^ > You said "now that I think about it, there was a desire to support hot- > unplug which also needed revoke". For us, hot unplug is done at the > device level and means all connections must be torn down. So in the > context of this argument, if people want revoke so DAX can migrate from > one NV-DIMM to another, ok. But revoke does not help RDMA migrate. > > If, instead, you mean that you want to support hot unplug of an NV-DIMM > that is currently the target of RDMA transfers, then I believe > Christoph's answer on this is correct. It all boils down to which > device you are talking about doing the hot unplug on.