[v2,01/11] iommu: Add new iommu op to create domains owned by userspace

From: Lu Baolu <baolu.lu@linux.intel.com>

Introduce a new iommu_domain op to create domains owned by userspace,
e.g. through iommufd. These domains have a few different properties
compares to kernel owned domains:

 - They may be UNMANAGED domains, but created with special parameters.
   For instance aperture size changes/number of levels, different
   IOPTE formats, or other things necessary to make a vIOMMU work

 - We have to track all the memory allocations with GFP_KERNEL_ACCOUNT
   to make the cgroup sandbox stronger

 - Device-specialty domains, such as NESTED domains can be created by
   iommufd.

The new op clearly says the domain is being created by IOMMUFD, that
the domain is intended for userspace use, and it provides a way to pass
a driver specific uAPI structure to customize the created domain to
exactly what the vIOMMU userspace driver requires.

iommu drivers that cannot support VFIO/IOMMUFD should not support this
op. This includes any driver that cannot provide a fully functional
UNMANAGED domain.

This op chooses to make the special parameters opaque to the core. This
suits the current usage model where accessing any of the IOMMU device
special parameters does require a userspace driver that matches the
kernel driver. If a need for common parameters, implemented similarly
by several drivers, arises then there is room in the design to grow a
generic parameter set as well.

This new op for now is only supposed to be used by iommufd, hence no
wrapper for it. iommufd would call the callback directly. As for domain
free, iommufd would use iommu_domain_free().

Also, add an op to return the length of supported user data structures
that must be added to include/uapi/include/iommufd.h file. This helps
the iommufd core to sanitize the input data before it forwards the data
to an iommu driver.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Co-developed-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
 include/linux/iommu.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

> From: Liu, Yi L <yi.l.liu@intel.com>
> Sent: Thursday, May 11, 2023 10:39 PM
> @@ -229,6 +238,15 @@ struct iommu_iotlb_gather {
>   *           after use. Return the data buffer if success, or ERR_PTR on
>   *           failure.
>   * @domain_alloc: allocate iommu domain
> + * @domain_alloc_user: allocate user iommu domain
> + * @domain_alloc_user_data_len: return the required length of the user
> data
> + *                              to allocate a specific type user iommu domain.
> + *                              @hwpt_type is defined as enum iommu_hwpt_type
> + *                              in include/uapi/linux/iommufd.h. The returned
> + *                              length is the corresponding sizeof driver data
> + *                              structures in include/uapi/linux/iommufd.h.
> + *                              -EOPNOTSUPP would be returned if the input
> + *                              @hwpt_type is not supported by the driver.

Can this be merged with earlier @hw_info callback? That will already
report a list of supported hwpt types. is there a problem to further
describe the data length for each type in that interface?

On Wed, May 24, 2023 at 06:41:41PM -0700, Nicolin Chen wrote:

> Upon a quick check, I think we could. Though it'd be slightly
> mismatched with the domain_alloc op, it should be fine since
> iommufd is likely to be the only caller.

Ideally the main op would return ERR_PTR too

Jason

On Tue, Jun 06, 2023 at 11:08:44AM -0300, Jason Gunthorpe wrote:
> On Wed, May 24, 2023 at 06:41:41PM -0700, Nicolin Chen wrote:
> 
> > Upon a quick check, I think we could. Though it'd be slightly
> > mismatched with the domain_alloc op, it should be fine since
> > iommufd is likely to be the only caller.
> 
> Ideally the main op would return ERR_PTR too

Yea. It just seems to be a bit painful to change it for that.

Worth a big series?

Thanks
Nic

On Tue, Jun 06, 2023 at 12:43:44PM -0700, Nicolin Chen wrote:
> On Tue, Jun 06, 2023 at 11:08:44AM -0300, Jason Gunthorpe wrote:
> > On Wed, May 24, 2023 at 06:41:41PM -0700, Nicolin Chen wrote:
> > 
> > > Upon a quick check, I think we could. Though it'd be slightly
> > > mismatched with the domain_alloc op, it should be fine since
> > > iommufd is likely to be the only caller.
> > 
> > Ideally the main op would return ERR_PTR too
> 
> Yea. It just seems to be a bit painful to change it for that.
> 
> Worth a big series?

Probably not..

Jason