From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [PATCH 5/5] vdpasim: vDPA device simulator Date: Tue, 4 Feb 2020 08:52:04 -0400 Message-ID: <20200204125204.GS23346@mellanox.com> References: <20200116124231.20253-1-jasowang@redhat.com> <20200116124231.20253-6-jasowang@redhat.com> <1b86d188-0666-f6ab-e3b3-bec1cfbd0c76@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Jason Wang Cc: Zhu Lingshan , mst@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, tiwei.bie@intel.com, maxime.coquelin@redhat.com, cunming.liang@intel.com, zhihong.wang@intel.com, rob.miller@broadcom.com, xiao.w.wang@intel.com, haotian.wang@sifive.com, lingshan.zhu@intel.com, eperezma@redhat.com, lulu@redhat.com, parav@mellanox.com, kevin.tian@intel.com, stefanha@redhat.com, rdunlap@infradead.org, hch@infradead.org, aadam@redhat.com, jakub.kicinski@netronome.com, jiri@mellanox.com, shahafs@mellanox.com, hanand@xilinx.com, mhabets@solarflare.com List-Id: virtualization@lists.linuxfoundation.org On Tue, Feb 04, 2020 at 04:28:27PM +0800, Jason Wang wrote: > > On 2020/2/4 下午4:21, Zhu Lingshan wrote: > > > +static const struct dma_map_ops vdpasim_dma_ops = { > > > +    .map_page = vdpasim_map_page, > > > +    .unmap_page = vdpasim_unmap_page, > > > +    .alloc = vdpasim_alloc_coherent, > > > +    .free = vdpasim_free_coherent, > > > +}; > > > + > > > > Hey Jason, > > > > IMHO, it would be nice if dma_ops of the parent device could be re-used. > > vdpa_device is expecting to represent a physical device except this > > simulator, however, there are not enough information in vdpa_device.dev > > to indicating which kind physical device it attached to. Namely > > get_arch_dma_ops(struct bus type) can not work on vdpa_device.dev. Then > > it seems device drivers need to implement a wrap of dma_ops of parent > > devices. Can this work be done in the vdpa framework since it looks like > > a common task? Can "vd_dev->vdev.dev.parent = vdpa->dev->parent;" in > > virtio_vdpa_probe() do the work? > > > > Thanks, > > BR > > Zhu Lingshan > > > Good catch. > > I think we can. IMHO you need to specify some 'dma_device', not try and play tricks with dma_ops, or assuming the parent is always the device used for dma. Jason