RE: [PATCH v5 12/15] vfio/type1: Add vSVA support for IOMMU-backed mdevs

["Liu, Yi L" <yi.l.liu@intel.com>]

Hi Eric,

> From: Auger Eric < eric.auger@redhat.com>
> Sent: Monday, July 20, 2020 8:22 PM
> 
> Yi,
> 
> On 7/12/20 1:21 PM, Liu Yi L wrote:
> > Recent years, mediated device pass-through framework (e.g. vfio-mdev)
> > is used to achieve flexible device sharing across domains (e.g. VMs).
> > Also there are hardware assisted mediated pass-through solutions from
> > platform vendors. e.g. Intel VT-d scalable mode which supports Intel
> > Scalable I/O Virtualization technology. Such mdevs are called IOMMU-
> > backed mdevs as there are IOMMU enforced DMA isolation for such mdevs.
> there is IOMMU enforced DMA isolation
> > In kernel, IOMMU-backed mdevs are exposed to IOMMU layer by aux-domain
> > concept, which means mdevs are protected by an iommu domain which is
> > auxiliary to the domain that the kernel driver primarily uses for DMA
> > API. Details can be found in the KVM presentation as below:
> >
> > https://events19.linuxfoundation.org/wp-content/uploads/2017/12/\
> > Hardware-Assisted-Mediated-Pass-Through-with-VFIO-Kevin-Tian-Intel.pdf
> >
> > This patch extends NESTING_IOMMU ops to IOMMU-backed mdev devices. The
> > main requirement is to use the auxiliary domain associated with mdev.
> 
> So as a result vSVM becomes functional for scalable mode mediated devices, right?

yes. as long as the mediated devices reports PASID capability.

> >
> > Cc: Kevin Tian <kevin.tian@intel.com>
> > CC: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > CC: Jun Tian <jun.j.tian@intel.com>
> > Cc: Alex Williamson <alex.williamson@redhat.com>
> > Cc: Eric Auger <eric.auger@redhat.com>
> > Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
> > Cc: Joerg Roedel <joro@8bytes.org>
> > Cc: Lu Baolu <baolu.lu@linux.intel.com>
> > Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
> > ---
> > v1 -> v2:
> > *) check the iommu_device to ensure the handling mdev is IOMMU-backed
> > ---
> >  drivers/vfio/vfio_iommu_type1.c | 39
> > +++++++++++++++++++++++++++++++++++----
> >  1 file changed, 35 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/vfio/vfio_iommu_type1.c
> > b/drivers/vfio/vfio_iommu_type1.c index 960cc59..f1f1ae2 100644
> > --- a/drivers/vfio/vfio_iommu_type1.c
> > +++ b/drivers/vfio/vfio_iommu_type1.c
> > @@ -2373,20 +2373,41 @@ static int vfio_iommu_resv_refresh(struct
> vfio_iommu *iommu,
> >  	return ret;
> >  }
> >
> > +static struct device *vfio_get_iommu_device(struct vfio_group *group,
> > +					    struct device *dev)
> > +{
> > +	if (group->mdev_group)
> > +		return vfio_mdev_get_iommu_device(dev);
> > +	else
> > +		return dev;
> > +}
> > +
> >  static int vfio_dev_bind_gpasid_fn(struct device *dev, void *data)  {
> >  	struct domain_capsule *dc = (struct domain_capsule *)data;
> >  	unsigned long arg = *(unsigned long *)dc->data;
> > +	struct device *iommu_device;
> > +
> > +	iommu_device = vfio_get_iommu_device(dc->group, dev);
> > +	if (!iommu_device)
> > +		return -EINVAL;
> >
> > -	return iommu_sva_bind_gpasid(dc->domain, dev, (void __user *)arg);
> > +	return iommu_sva_bind_gpasid(dc->domain, iommu_device,
> > +				     (void __user *)arg);
> >  }
> >
> >  static int vfio_dev_unbind_gpasid_fn(struct device *dev, void *data)
> > {
> >  	struct domain_capsule *dc = (struct domain_capsule *)data;
> >  	unsigned long arg = *(unsigned long *)dc->data;
> > +	struct device *iommu_device;
> >
> > -	iommu_sva_unbind_gpasid(dc->domain, dev, (void __user *)arg);
> > +	iommu_device = vfio_get_iommu_device(dc->group, dev);
> > +	if (!iommu_device)
> > +		return -EINVAL;
> > +
> > +	iommu_sva_unbind_gpasid(dc->domain, iommu_device,
> > +				(void __user *)arg);
> >  	return 0;
> >  }
> >
> > @@ -2395,8 +2416,13 @@ static int __vfio_dev_unbind_gpasid_fn(struct device
> *dev, void *data)
> >  	struct domain_capsule *dc = (struct domain_capsule *)data;
> >  	struct iommu_gpasid_bind_data *unbind_data =
> >  				(struct iommu_gpasid_bind_data *)dc->data;
> > +	struct device *iommu_device;
> > +
> > +	iommu_device = vfio_get_iommu_device(dc->group, dev);
> > +	if (!iommu_device)
> > +		return -EINVAL;
> >
> > -	__iommu_sva_unbind_gpasid(dc->domain, dev, unbind_data);
> > +	__iommu_sva_unbind_gpasid(dc->domain, iommu_device, unbind_data);
> >  	return 0;
> >  }
> >
> > @@ -3077,8 +3103,13 @@ static int vfio_dev_cache_invalidate_fn(struct
> > device *dev, void *data)  {
> >  	struct domain_capsule *dc = (struct domain_capsule *)data;
> >  	unsigned long arg = *(unsigned long *)dc->data;
> > +	struct device *iommu_device;
> > +
> > +	iommu_device = vfio_get_iommu_device(dc->group, dev);
> > +	if (!iommu_device)
> > +		return -EINVAL;
> >
> > -	iommu_cache_invalidate(dc->domain, dev, (void __user *)arg);
> > +	iommu_cache_invalidate(dc->domain, iommu_device, (void __user
> > +*)arg);
> >  	return 0;
> >  }
> >
> >
> Besides,
> 
> Looks grood to me
> 
> Reviewed-by: Eric Auger <eric.auger@redhat.com>

thanks :-)

Regards,
Yi Liu

> Eric

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