Hi Alex, > From: Alex Williamson <alex.williamson@xxxxxxxxxx> > Sent: Friday, April 3, 2020 4:34 AM > To: Liu, Yi L <yi.l.liu@xxxxxxxxx> > Subject: Re: [PATCH v1 8/8] vfio/type1: Add vSVA support for IOMMU-backed > mdevs > > On Sun, 22 Mar 2020 05:32:05 -0700 > "Liu, Yi L" <yi.l.liu@xxxxxxxxx> wrote: > > > From: Liu Yi L <yi.l.liu@xxxxxxxxx> > > > > Recent years, mediated device pass-through framework (e.g. vfio-mdev) > > are 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. > > 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 > > aux-domain of its physical device. Details can be found in the KVM > > presentation from Kevin Tian. IOMMU-backed equals to IOMMU-capable. > > > > https://events19.linuxfoundation.org/wp-content/uploads/2017/12/\ > > Hardware-Assisted-Mediated-Pass-Through-with-VFIO-Kevin-Tian-Intel.pdf > > > > This patch supports NESTING IOMMU for IOMMU-backed mdevs by figuring > > out the physical device of an IOMMU-backed mdev and then invoking IOMMU > > requests to IOMMU layer with the physical device and the mdev's aux > > domain info. > > > > With this patch, vSVA (Virtual Shared Virtual Addressing) can be used > > on IOMMU-backed mdevs. > > > > Cc: Kevin Tian <kevin.tian@xxxxxxxxx> > > CC: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx> > > CC: Jun Tian <jun.j.tian@xxxxxxxxx> > > Cc: Alex Williamson <alex.williamson@xxxxxxxxxx> > > Cc: Eric Auger <eric.auger@xxxxxxxxxx> > > Cc: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx> > > Signed-off-by: Liu Yi L <yi.l.liu@xxxxxxxxx> > > --- > > drivers/vfio/vfio_iommu_type1.c | 23 ++++++++++++++++++++--- > > 1 file changed, 20 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > > index 937ec3f..d473665 100644 > > --- a/drivers/vfio/vfio_iommu_type1.c > > +++ b/drivers/vfio/vfio_iommu_type1.c > > @@ -132,6 +132,7 @@ struct vfio_regions { > > > > struct domain_capsule { > > struct iommu_domain *domain; > > + struct vfio_group *group; > > void *data; > > }; > > > > @@ -148,6 +149,7 @@ static int vfio_iommu_for_each_dev(struct vfio_iommu > *iommu, > > list_for_each_entry(d, &iommu->domain_list, next) { > > dc.domain = d->domain; > > list_for_each_entry(g, &d->group_list, next) { > > + dc.group = g; > > ret = iommu_group_for_each_dev(g->iommu_group, > > &dc, fn); > > if (ret) > > @@ -2347,7 +2349,12 @@ static int vfio_bind_gpasid_fn(struct device *dev, void > *data) > > struct iommu_gpasid_bind_data *gbind_data = > > (struct iommu_gpasid_bind_data *) dc->data; > > > > - return iommu_sva_bind_gpasid(dc->domain, dev, gbind_data); > > + if (dc->group->mdev_group) > > + return iommu_sva_bind_gpasid(dc->domain, > > + vfio_mdev_get_iommu_device(dev), gbind_data); > > But we can't assume an mdev device is iommu backed, so this can call > with NULL dev, which appears will pretty quickly segfault > intel_svm_bind_gpasid. I don't think the non-iommu backed mdev will not be in the iommu->domain_list. right? But, yeah, from this function p.o.v , it is still necessary to do a check. How about adding a check on the return of vfio_mdev_get_iommu_device(dev)? If iommu_device is fetch, the mdev should be iommu-backed. does it make sense? Regards, Yi Liu > > > + else > > + return iommu_sva_bind_gpasid(dc->domain, > > + dev, gbind_data); > > } > > > > static int vfio_unbind_gpasid_fn(struct device *dev, void *data) > > @@ -2356,8 +2363,13 @@ static int vfio_unbind_gpasid_fn(struct device *dev, > void *data) > > struct iommu_gpasid_bind_data *gbind_data = > > (struct iommu_gpasid_bind_data *) dc->data; > > > > - return iommu_sva_unbind_gpasid(dc->domain, dev, > > + if (dc->group->mdev_group) > > + return iommu_sva_unbind_gpasid(dc->domain, > > + vfio_mdev_get_iommu_device(dev), > > gbind_data->hpasid); > > Same > > > + else > > + return iommu_sva_unbind_gpasid(dc->domain, dev, > > + gbind_data->hpasid); > > } > > > > /** > > @@ -2429,7 +2441,12 @@ static int vfio_cache_inv_fn(struct device *dev, void > *data) > > struct iommu_cache_invalidate_info *cache_inv_info = > > (struct iommu_cache_invalidate_info *) dc->data; > > > > - return iommu_cache_invalidate(dc->domain, dev, cache_inv_info); > > + if (dc->group->mdev_group) > > + return iommu_cache_invalidate(dc->domain, > > + vfio_mdev_get_iommu_device(dev), cache_inv_info); > > And again > > > + else > > + return iommu_cache_invalidate(dc->domain, > > + dev, cache_inv_info); > > } > > > > static long vfio_iommu_type1_ioctl(void *iommu_data,
