On Thu, 27 Oct 2016 18:01:51 +0530 Kirti Wankhede <kwankh...@nvidia.com> wrote:
> On 10/27/2016 12:50 PM, Alexey Kardashevskiy wrote: > > On 18/10/16 08:22, Kirti Wankhede wrote: > >> VFIO IOMMU drivers are designed for the devices which are IOMMU capable. > >> Mediated device only uses IOMMU APIs, the underlying hardware can be > >> managed by an IOMMU domain. > >> > >> Aim of this change is: > >> - To use most of the code of TYPE1 IOMMU driver for mediated devices > >> - To support direct assigned device and mediated device in single module > >> > >> Added two new callback functions to struct vfio_iommu_driver_ops. Backend > >> IOMMU module that supports pining and unpinning pages for mdev devices > >> should provide these functions. > >> Added APIs for pining and unpining pages to VFIO module. These calls back > >> into backend iommu module to actually pin and unpin pages. > >> > >> This change adds pin and unpin support for mediated device to TYPE1 IOMMU > >> backend module. More details: > >> - When iommu_group of mediated devices is attached, task structure is > >> cached which is used later to pin pages and page accounting. > > > > > > For SPAPR TCE IOMMU driver, I ended up caching mm_struct with > > atomic_inc(&container->mm->mm_count) (patches are on the way) instead of > > using @current or task as the process might be gone while VFIO container is > > still alive and @mm might be needed to do proper cleanup; this might not be > > an issue with this patchset now but still you seem to only use @mm from > > task_struct. > > > > Consider the example of QEMU process which creates VFIO container, QEMU > in its teardown path would release the container. How could container be > alive when process is gone? If QEMU is sent a SIGKILL, does the process still exist? We must be able to perform cleanup regardless of the state, or existence, of the task that created it. Thanks, Alex
