On 10/27/2016 8:00 PM, Alex Williamson wrote: > 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, >
The kernel closes all open file descriptors when any process is terminated, so .release() from struct vfio_iommu_driver_ops gets called on SIGKILL or SIGTERM and release() function do all cleanup. Kirti
