On 27/10/16 23:31, Kirti Wankhede 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? do_exit() in kernel/exit.c calls exit_mm() (which sets NULL to tsk->mm) first, and then releases open files by calling exit_files(). So container's release() does not have current->mm. > > Kirti > >> >> >>> - It keeps track of pinned pages for mediated domain. This data is used to >>> verify unpinning request and to unpin remaining pages while detaching, if >>> there are any. >>> - Used existing mechanism for page accounting. If iommu capable domain >>> exist in the container then all pages are already pinned and accounted. >>> Accouting for mdev device is only done if there is no iommu capable >>> domain in the container. >>> - Page accouting is updated on hot plug and unplug mdev device and pass >>> through device. >>> >>> Tested by assigning below combinations of devices to a single VM: >>> - GPU pass through only >>> - vGPU device only >>> - One GPU pass through and one vGPU device >>> - Linux VM hot plug and unplug vGPU device while GPU pass through device >>> exist >>> - Linux VM hot plug and unplug GPU pass through device while vGPU device >>> exist >>> >>> Signed-off-by: Kirti Wankhede <kwankhede@xxxxxxxxxx> >>> Signed-off-by: Neo Jia <cjia@xxxxxxxxxx> >>> Change-Id: I295d6f0f2e0579b8d9882bfd8fd5a4194b97bd9a >> >> -- Alexey -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
