Re: [PATCH v4 04/18] iommu: Add iommu_domain ops for dirty tracking

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, Oct 18, 2023 at 09:27:01PM +0100, Joao Martins wrote:
> Add to iommu domain operations a set of callbacks to perform dirty
> tracking, particulary to start and stop tracking and to read and clear the
> dirty data.
> 
> Drivers are generally expected to dynamically change its translation
> structures to toggle the tracking and flush some form of control state
> structure that stands in the IOVA translation path. Though it's not
> mandatory, as drivers can also enable dirty tracking at boot, and just
> clear the dirty bits before setting dirty tracking. For each of the newly
> added IOMMU core APIs:
> 
> iommu_cap::IOMMU_CAP_DIRTY: new device iommu_capable value when probing for
> capabilities of the device.
> 
> .set_dirty_tracking(): an iommu driver is expected to change its
> translation structures and enable dirty tracking for the devices in the
> iommu_domain. For drivers making dirty tracking always-enabled, it should
> just return 0.
> 
> .read_and_clear_dirty(): an iommu driver is expected to walk the pagetables
> for the iova range passed in and use iommu_dirty_bitmap_record() to record
> dirty info per IOVA. When detecting that a given IOVA is dirty it should
> also clear its dirty state from the PTE, *unless* the flag
> IOMMU_DIRTY_NO_CLEAR is passed in -- flushing is steered from the caller of
> the domain_op via iotlb_gather. The iommu core APIs use the same data
> structure in use for dirty tracking for VFIO device dirty (struct
> iova_bitmap) abstracted by iommu_dirty_bitmap_record() helper function.
> 
> domain::dirty_ops: IOMMU domains will store the dirty ops depending on
> whether the iommu device supports dirty tracking or not. iommu drivers can
> then use this field to figure if the dirty tracking is supported+enforced
> on attach. The enforcement is enable via domain_alloc_user() which is done
> via IOMMUFD hwpt flag introduced later.
> 
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> ---
>  include/linux/io-pgtable.h |  4 +++
>  include/linux/iommu.h      | 56 ++++++++++++++++++++++++++++++++++++++
>  2 files changed, 60 insertions(+)

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

Jason