Re: [Qemu-devel] [PATCH v9 04/12] vfio iommu: Add support for mediated devices

[Alex Williamson]

On Fri, 21 Oct 2016 15:49:07 +0800
Jike Song <address@hidden> wrote:

> On 10/18/2016 05:22 AM, Kirti Wankhede wrote:
> > diff --git a/drivers/vfio/vfio_iommu_type1.c 
> > b/drivers/vfio/vfio_iommu_type1.c
> > index 2ba19424e4a1..5d67058a611d 100644
> > --- a/drivers/vfio/vfio_iommu_type1.c
> > +++ b/drivers/vfio/vfio_iommu_type1.c  
> [snip]
> >  static int vfio_iommu_type1_attach_group(void *iommu_data,
> >                                      struct iommu_group *iommu_group)
> >  {
> >     struct vfio_iommu *iommu = iommu_data;
> > -   struct vfio_group *group, *g;
> > +   struct vfio_group *group;
> >     struct vfio_domain *domain, *d;
> >     struct bus_type *bus = NULL;
> >     int ret;
> > @@ -746,10 +1136,14 @@ static int vfio_iommu_type1_attach_group(void 
> > *iommu_data,
> >     mutex_lock(&iommu->lock);
> >  
> >     list_for_each_entry(d, &iommu->domain_list, next) {
> > -           list_for_each_entry(g, &d->group_list, next) {
> > -                   if (g->iommu_group != iommu_group)
> > -                           continue;
> > +           if (find_iommu_group(d, iommu_group)) {
> > +                   mutex_unlock(&iommu->lock);
> > +                   return -EINVAL;
> > +           }
> > +   }
> >  
> > +   if (iommu->local_domain) {
> > +           if (find_iommu_group(iommu->local_domain, iommu_group)) {
> >                     mutex_unlock(&iommu->lock);
> >                     return -EINVAL;
> >             }
> > @@ -769,6 +1163,30 @@ static int vfio_iommu_type1_attach_group(void 
> > *iommu_data,
> >     if (ret)
> >             goto out_free;
> >  
> > +   if (IS_ENABLED(CONFIG_VFIO_MDEV) && !iommu_present(bus) &&
> > +       (bus == &mdev_bus_type)) {  
> 
> Hi Kirti,
> 
> By refering mdev_bus_type directly you are making vfio_iommu_type1.ko depends
> on mdev.ko, but in Kconfig doesn't guarantee the dependency. For example,
> if CONFIG_VFIO_IOMMU_TYPE1=y and CONFIG_VFIO_MDEV=m, the building will fail.

Good point, Jike.  I don't think we want to make existing vfio modules
dependent on mdev modules.  I wonder if we can lookup the mdev_bus_type
symbol w/o triggering the module load.  Thanks,

Alex