Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S980805AbdDYGbj convert rfc822-to-8bit (ORCPT ); Tue, 25 Apr 2017 02:31:39 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:47216 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S941644AbdDYGbb (ORCPT ); Tue, 25 Apr 2017 02:31:31 -0400 Message-ID: <1493101803.3171.246.camel@oracle.com> Subject: Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory From: Knut Omang To: Logan Gunthorpe , Benjamin Herrenschmidt , Dan Williams Cc: Bjorn Helgaas , Jason Gunthorpe , Christoph Hellwig , Sagi Grimberg , "James E.J. Bottomley" , "Martin K. Petersen" , Jens Axboe , Steve Wise , Stephen Bates , Max Gurtovoy , Keith Busch , linux-pci@vger.kernel.org, linux-scsi , linux-nvme@lists.infradead.org, linux-rdma@vger.kernel.org, linux-nvdimm , "linux-kernel@vger.kernel.org" , Jerome Glisse Date: Tue, 25 Apr 2017 08:30:03 +0200 In-Reply-To: <9b6c0830-a728-c7ca-e6c6-2135f3f760ed@deltatee.com> References: <1490911959-5146-1-git-send-email-logang@deltatee.com> <1491974532.7236.43.camel@kernel.crashing.org> <5ac22496-56ec-025d-f153-140001d2a7f9@deltatee.com> <1492034124.7236.77.camel@kernel.crashing.org> <81888a1e-eb0d-cbbc-dc66-0a09c32e4ea2@deltatee.com> <20170413232631.GB24910@bhelgaas-glaptop.roam.corp.google.com> <20170414041656.GA30694@obsidianresearch.com> <1492169849.25766.3.camel@kernel.crashing.org> <630c1c63-ff17-1116-e069-2b8f93e50fa2@deltatee.com> <20170414190452.GA15679@bhelgaas-glaptop.roam.corp.google.com> <1492207643.25766.18.camel@kernel.crashing.org> <1492311719.25766.37.camel@kernel.crashing.org> <5e43818e-8c6b-8be8-23ff-b798633d2a73@deltatee.com> <1492381907.25766.49.camel@kernel.crashing.org> <1493019397.3171.118.camel@oracle.com> <9b6c0830-a728-c7ca-e6c6-2135f3f760ed@deltatee.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.20.5 (3.20.5-1.fc24) Mime-Version: 1.0 Content-Transfer-Encoding: 8BIT X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1321 Lines: 31 On Mon, 2017-04-24 at 10:14 -0600, Logan Gunthorpe wrote: > > On 24/04/17 01:36 AM, Knut Omang wrote: > > My first reflex when reading this thread was to think that this whole domain > > lends it self excellently to testing via Qemu. Could it be that doing this in  > > the opposite direction might be a safer approach in the long run even though  > > (significant) more work up-front? > > That's an interesting idea. We did do some very limited testing on qemu > with one iteration of our work. However, it's difficult because there is > no support for any RDMA devices which are a part of our primary use > case. Yes, that's why I used 'significant'. One good thing is that given resources  it can easily be done in parallel with other development, and will give additional insight of some form. > I also imagine it would be quite difficult to develop those models > given the array of hardware that needs to be supported and the deep > functional knowledge required to figure out appropriate restrictions. >From my naive perspective it seems it need not even be a full model to get some benefits, just low level functionality tests with some instances of a device that offers some MMIO space 'playground'. Or maybe you can leverage some of the already implemented emulated devices in Qemu? Knut > > Logan