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SubjectRe: [PATCH v8 7/9] vfio/mdev: Add iommu related member in mdev_device
On Wed, 27 Mar 2019 14:17:57 +0000
Parav Pandit <parav@mellanox.com> wrote:

> > -----Original Message-----
> > From: linux-kernel-owner@vger.kernel.org <linux-kernel-
> > owner@vger.kernel.org> On Behalf Of Kirti Wankhede
> > Sent: Tuesday, March 26, 2019 4:33 AM
> > To: Lu Baolu <baolu.lu@linux.intel.com>; Joerg Roedel <joro@8bytes.org>;
> > David Woodhouse <dwmw2@infradead.org>; Alex Williamson
> > <alex.williamson@redhat.com>
> > Cc: ashok.raj@intel.com; sanjay.k.kumar@intel.com;
> > jacob.jun.pan@intel.com; kevin.tian@intel.com; Jean-Philippe Brucker <jean-
> > philippe.brucker@arm.com>; yi.l.liu@intel.com; yi.y.sun@intel.com;
> > peterx@redhat.com; tiwei.bie@intel.com; xin.zeng@intel.com;
> > iommu@lists.linux-foundation.org; kvm@vger.kernel.org; linux-
> > kernel@vger.kernel.org; Jacob Pan <jacob.jun.pan@linux.intel.com>; Neo Jia
> > <cjia@nvidia.com>
> > Subject: Re: [PATCH v8 7/9] vfio/mdev: Add iommu related member in
> > mdev_device
> >
> >
> >
> > On 3/25/2019 7:00 AM, Lu Baolu wrote:
> > > A parent device might create different types of mediated devices. For
> > > example, a mediated device could be created by the parent device with
> > > full isolation and protection provided by the IOMMU. One usage case
> > > could be found on Intel platforms where a mediated device is an
> > > assignable subset of a PCI, the DMA requests on behalf of it are all
> > > tagged with a PASID. Since IOMMU supports PASID-granular translations
> > > (scalable mode in VT-d 3.0), this mediated device could be
> > > individually protected and isolated by an IOMMU.
> > >
> > > This patch adds a new member in the struct mdev_device to indicate
> > > that the mediated device represented by mdev could be isolated and
> > > protected by attaching a domain to a device represented by
> > > mdev->iommu_device. It also adds a helper to add or set the iommu
> > > device.
> > >
> > > * mdev_device->iommu_device
> > > - This, if set, indicates that the mediated device could
> > > be fully isolated and protected by IOMMU via attaching
> > > an iommu domain to this device. If empty, it indicates
> > > using vendor defined isolation, hence bypass IOMMU.
> > >
> > > * mdev_set/get_iommu_device(dev, iommu_device)
> > > - Set or get the iommu device which represents this mdev
> > > in IOMMU's device scope. Drivers don't need to set the
> > > iommu device if it uses vendor defined isolation.
> > >
> > > Cc: Ashok Raj <ashok.raj@intel.com>
> > > Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > > Cc: Kevin Tian <kevin.tian@intel.com>
> > > Cc: Liu Yi L <yi.l.liu@intel.com>
> > > Suggested-by: Kevin Tian <kevin.tian@intel.com>
> > > Suggested-by: Alex Williamson <alex.williamson@redhat.com>
> > > Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> > > Reviewed-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
> > > ---
> > > drivers/vfio/mdev/mdev_core.c | 18 ++++++++++++++++++
> > > drivers/vfio/mdev/mdev_private.h | 1 +
> > > include/linux/mdev.h | 14 ++++++++++++++
> > > 3 files changed, 33 insertions(+)
> > >
> > > diff --git a/drivers/vfio/mdev/mdev_core.c
> > > b/drivers/vfio/mdev/mdev_core.c index b96fedc77ee5..1b6435529166
> > > 100644
> > > --- a/drivers/vfio/mdev/mdev_core.c
> > > +++ b/drivers/vfio/mdev/mdev_core.c
> > > @@ -390,6 +390,24 @@ int mdev_device_remove(struct device *dev, bool
> > force_remove)
> > > return 0;
> > > }
> > >
> > > +int mdev_set_iommu_device(struct device *dev, struct device
> > > +*iommu_device) {
> > > + struct mdev_device *mdev = to_mdev_device(dev);
> > > +
> > > + mdev->iommu_device = iommu_device;
> > > +
> > > + return 0;
> > > +}
> > > +EXPORT_SYMBOL(mdev_set_iommu_device);
> > > +
> > > +struct device *mdev_get_iommu_device(struct device *dev) {
> > > + struct mdev_device *mdev = to_mdev_device(dev);
> > > +
> > > + return mdev->iommu_device;
> > > +}
> > > +EXPORT_SYMBOL(mdev_get_iommu_device);
> > > +
> > > static int __init mdev_init(void)
> > > {
> > > return mdev_bus_register();
> > > diff --git a/drivers/vfio/mdev/mdev_private.h
> > > b/drivers/vfio/mdev/mdev_private.h
> > > index 379758c52b1b..bfb7b22a7cb6 100644
> > > --- a/drivers/vfio/mdev/mdev_private.h
> > > +++ b/drivers/vfio/mdev/mdev_private.h
> > > @@ -34,6 +34,7 @@ struct mdev_device {
> > > struct list_head next;
> > > struct kobject *type_kobj;
> > > bool active;
> > > + struct device *iommu_device;
> > > };
> > >
> This is not a performance path, but it is a good practice to create naturally aligned/packed structures.
> You should define struct device *iommu_device; before bool active.

Agreed, if someone wants to fixup before commit or if there's another
spin please do so, otherwise we can adjust it in a trivial follow-up
patch. Thanks,

Alex

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