> -----Original Message----- > From: Alex Williamson [mailto:[email protected]] > Sent: Saturday, January 18, 2014 1:39 AM > To: Sethi Varun-B16395 > Cc: [email protected]; [email protected]; linux- > [email protected] > Subject: Re: [RFC][PATCH] Remove bus dependency for iommu_domain_alloc. > > On Sat, 2014-01-18 at 01:00 +0530, Varun Sethi wrote: > > This patch attempts to remove iommu_domain_alloc function's dependency > on the bus type. > > This dependency is quiet restrictive in case of vfio, where it's > > possible to bind multiple iommu groups (from different bus types) to > the same iommu domain. > > > > This patch is based on the assumption, that there is a single iommu > > for all bus types on the system. > > > > We maintain a list of bus types (for which iommu ops are registered). > > In the iommu_domain_alloc function we ensure that all bus types > correspond to the same set of iommu operations. > > Seems like this just kicks the problem down the road a little ways as I > expect the assumption isn't going to last long. I think there's another > way to do this and we can do it entirely from within vfio_iommu_type1. > We have a problem on x86 that the IOMMU driver can be backed by multiple > IOMMU hardware devices. These separate devices are architecturally > allowed to have different properties. The property causing us trouble is > cache coherency. Some hardware devices allow us to use IOMMU_CACHE as a > mapping attribute, others do not. Therefore we cannot use a single IOMMU > domain to optimally handle all devices in a heterogeneous environment. > > I think the solution to this is to have vfio_iommu_type1 transparently > support multiple IOMMU domains. In the implementation of that, it seems > to make sense to move the iommu_domain_alloc() to the point where we > attach a group to the domain. That means we can scan the devices in the [Sethi Varun-B16395] Multiple iommu groups can also share the same domain (as a part Of the same VFIO container). I am not sure how can we handle the case of iommu groups from Different bus types in vfio.
-Varun > domain to determine the bus. I suppose there is still an assumption that > all the devices in a group are on the same bus, but since the group is > determined by the IOMMU and we already assume only a single IOMMU per > bus, I think we're ok. I spent some time working on a patch to do this, > but it isn't quite finished. I'll try to bandage the rough edges and > send it out as an RFC so you can see what I'm talking about. Thanks, > > Alex > > > Signed-off-by: Varun Sethi <[email protected]> > > --- > > arch/arm/mm/dma-mapping.c | 2 +- > > drivers/gpu/drm/msm/msm_gpu.c | 2 +- > > drivers/iommu/amd_iommu_v2.c | 2 +- > > drivers/iommu/iommu.c | 32 > +++++++++++++++++++++++++++++--- > > drivers/media/platform/omap3isp/isp.c | 2 +- > > drivers/remoteproc/remoteproc_core.c | 2 +- > > drivers/vfio/vfio_iommu_type1.c | 2 +- > > include/linux/device.h | 2 ++ > > include/linux/iommu.h | 4 ++-- > > virt/kvm/iommu.c | 2 +- > > 10 files changed, 40 insertions(+), 12 deletions(-) N�����r��y����b�X��ǧv�^�){.n�+����{����zX����ܨ}���Ơz�&j:+v�������zZ+��+zf���h���~����i���z� �w���?�����&�)ߢf��^jǫy�m��@A�a��� 0��h���i
