From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: 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" Mime-Version: 1.0 List-ID: On Mon, 2017-04-24 at 10:14 -0600, Logan Gunthorpe wrote: >=20 > On 24/04/17 01:36 AM, Knut Omang wrote: > > My first reflex when reading this thread was to think that this whole d= omain > > lends it self excellently to testing via Qemu. Could it be that doing t= his in=C2=A0 > > the opposite direction might be a safer approach in the long run even t= hough=C2=A0 > > (significant) more work up-front? >=20 > 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.=20 Yes, that's why I used 'significant'. One good thing is that given resource= s=C2=A0 it can easily be done in parallel with other development, and will give add= itional 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 >=20 > Logan