From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [RFC PATCH 00/28] Removing struct page from P2PDMA Date: Thu, 27 Jun 2019 11:01:54 +0200 Message-ID: <20190627090154.GA11548@lst.de> References: <20190620161240.22738-1-logang@deltatee.com> <20190624072752.GA3954@lst.de> <558a27ba-e7c9-9d94-cad0-377b8ee374a6@deltatee.com> <20190625072008.GB30350@lst.de> <20190625170115.GA9746@lst.de> <41235a05-8ed1-e69a-e7cd-48cae7d8a676@deltatee.com> <20190626065708.GB24531@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Logan Gunthorpe Cc: Christoph Hellwig , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, linux-pci@vger.kernel.org, linux-rdma@vger.kernel.org, Jens Axboe , Bjorn Helgaas , Dan Williams , Sagi Grimberg , Keith Busch , Jason Gunthorpe , Stephen Bates List-Id: linux-rdma@vger.kernel.org On Wed, Jun 26, 2019 at 12:31:08PM -0600, Logan Gunthorpe wrote: > > we have a hole behind len where we could store flag. Preferably > > optionally based on a P2P or other magic memory types config > > option so that 32-bit systems with 32-bit phys_addr_t actually > > benefit from the smaller and better packing structure. > > That seems sensible. The one thing that's unclear though is how to get > the PCI Bus address when appropriate. Can we pass that in instead of the > phys_addr with an appropriate flag? Or will we need to pass the actual > physical address and then, at the map step, the driver has to some how > lookup the PCI device to figure out the bus offset? Yes, I think we'll need a lookup mechanism of some kind.