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

From: Alex Williamson
Date: Fri Oct 21 2016 - 10:36:09 EST


On Fri, 21 Oct 2016 15:49:07 +0800
Jike Song <jike.song@xxxxxxxxx> 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