From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [PATCH v7 07/12] dma-mapping: introduce dma_has_iommu() Date: Mon, 9 Oct 2017 12:58:40 -0600 Message-ID: <20171009185840.GB15336@obsidianresearch.com> References: <150732931273.22363.8436792888326501071.stgit@dwillia2-desk3.amr.corp.intel.com> <150732935473.22363.1853399637339625023.stgit@dwillia2-desk3.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <150732935473.22363.1853399637339625023.stgit-p8uTFz9XbKj2zm6wflaqv1nYeNYlB/vhral2JQCrhuEAvxtiuMwx3w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" To: Dan Williams Cc: Jan Kara , Ashok Raj , "Darrick J. Wong" , linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Greg Kroah-Hartman , Joerg Roedel , linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org, Dave Chinner , Robin Murphy , linux-xfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, David Woodhouse , Christoph Hellwig , Marek Szyprowski List-Id: linux-api@vger.kernel.org On Fri, Oct 06, 2017 at 03:35:54PM -0700, Dan Williams wrote: > otherwise be quiesced. The need for this knowledge is driven by a need > to make RDMA transfers to DAX mappings safe. If the DAX file's block map > changes we need to be to reliably stop accesses to blocks that have been > freed or re-assigned to a new file. If RDMA is driving this need, why not invalidate backing RDMA MRs instead of requiring a IOMMU to do it? RDMA MR are finer grained and do not suffer from the re-use problem David W. brought up with IOVAs.. Jason