Re: [PATCH 5/5] vdpasim: vDPA device simulator

[Jason Wang]

On 2020/2/4 äå8:52, Jason Gunthorpe wrote:
> On Tue, Feb 04, 2020 at 04:28:27PM +0800, Jason Wang wrote:
> > On 2020/2/4 äå4:21, Zhu Lingshan wrote:
> > > > +static const struct dma_map_ops vdpasim_dma_ops = {
> > > > +ÂÂÂ .map_page = vdpasim_map_page,
> > > > +ÂÂÂ .unmap_page = vdpasim_unmap_page,
> > > > +ÂÂÂ .alloc = vdpasim_alloc_coherent,
> > > > +ÂÂÂ .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


Right, this is what in my mind and discussed in the vhost-vdpa thread.

Will go this way.

Thanks