On Thu, 18 Aug 2016 16:42:14 +0800 Dong Jia <bjsdj...@linux.vnet.ibm.com> wrote:
> On Wed, 17 Aug 2016 03:09:10 -0700 > Neo Jia <c...@nvidia.com> wrote: > > > On Wed, Aug 17, 2016 at 04:58:14PM +0800, Dong Jia wrote: > > > On Tue, 16 Aug 2016 16:14:12 +0800 > > > Jike Song <jike.s...@intel.com> wrote: > > > > > > > > > > > This patchset is based on NVidia's "Add Mediated device support" > > > > series, version 6: > > > > > > > > http://www.spinics.net/lists/kvm/msg136472.html > > > > > > > > > > > > Background: > > > > > > > > The patchset from NVidia introduced the Mediated Device support > > > > to > > > > Linux/VFIO. With that series, one can create virtual devices > > > > (supporting > > > > by underlying physical device and vendor driver), and assign > > > > them to > > > > userspace like QEMU/KVM, in the same way as device assignment > > > > via VFIO. > > > > > > > > Based on that, NVidia and Intel implemented their vGPU > > > > solutions, IBM > > > > implemented its CCW pass-through. However, there are > > > > limitations > > > > imposed by current (v6 in particular) mdev framework: the mdev > > > > must be > > > > represented as a PCI device, several vfio capabilities such as > > > > sparse mmap are not possible, and so forth. > > > > > > > > This series aims to address above limitations and simplify the > > > > implementation. > > > > > > > > > > > > Key Changes: > > > > > > > > - An independent "struct device" was introduced to > > > > parent_device, thus > > > > a hierarchy in driver core is formed with physical device, > > > > parent device > > > > and mdev device; > > > > > > > > - Leveraging the mechanism and APIs provided by Linux driver > > > > core, it > > > > is now safe to remove all refcnts and locks; > > > > > > > > - vfio_mpci (later renamed to vfio_mdev) was made BUS-agnostic: > > > > all > > > > PCI-specific logic was removed, accesses from userspace are > > > > now > > > > passed to vendor driver directly, thus guaranteed that full > > > > VFIO > > > > capabilities provided: e.g. dynamic regions, sparse mmap, > > > > etc.; > > > > > > > > With vfio_mdev being BUS-agnostic, it is enough to have only > > > > one > > > > driver for all mdev devices; > > > > > > Hi Jike: > > > > > > I don't know what happened, but finding out which direction this will > > > likely go seems my first priority now... > > > > Hi Dong, > > > > Just want to let you know that we are preparing the v7 patches to > > incorporate > > the latest review comments from Intel folks and Alex, for some changes in > > this > > patch set also mentioned in the recent review are already queued up in the > > new > > version. > Hi Neo, > > Good to know this. :> > > > > > > > > > I'd say, either with only the original mdev v6, or patched this series, > > > vfio-ccw could live. But this series saves my work of mimicing the > > > vfio-mpci code in my vfio-mccw driver. I like this incremental patches. > > > > Thanks for sharing your progress and good to know our current v6 solution > > works > > for you. We are still evaluating the vfio_mdev changes here as I still > > prefer to > > share general VFIO pci handling inside a common VFIO PCI driver, and the > > modularization will reduce the impact of future changes and potential > > regressions > > cross architectures - between PCI and CCW. > If this is something that Alex and the Intel folks are fine with, I have > no problem with this too. Thanks, Overall, I like this a lot. Creating a proper device hierarchy and letting the driver core manage the references makes a lot of sense and the reduction in code volume and complexity speaks for itself. I like how the PCI mdev layer goes away, we're not imposing arbitrary restrictions on the vendor driver in an attempt to insert a common layer. We can add helpers for things that do end up being common as we go. Using devices rather than uuids for functions is a big improvement. I hope that Neo and Kirti will incorporate many of these changes in their next revision. Thanks for stepping in with this, Alex
