On Fri, Dec 08, 2023 at 01:57:26PM +0800, Baolu Lu wrote: > On 12/1/23 10:24 PM, Jason Gunthorpe wrote: > > On Thu, Oct 26, 2023 at 10:49:24AM +0800, Lu Baolu wrote: > > > Hi folks, > > > > > > This series implements the functionality of delivering IO page faults to > > > user space through the IOMMUFD framework for nested translation. Nested > > > translation is a hardware feature that supports two-stage translation > > > tables for IOMMU. The second-stage translation table is managed by the > > > host VMM, while the first-stage translation table is owned by user > > > space. This allows user space to control the IOMMU mappings for its > > > devices. > > > > > > When an IO page fault occurs on the first-stage translation table, the > > > IOMMU hardware can deliver the page fault to user space through the > > > IOMMUFD framework. User space can then handle the page fault and respond > > > to the device top-down through the IOMMUFD. This allows user space to > > > implement its own IO page fault handling policies. > > > > > > User space indicates its capability of handling IO page faults by > > > setting the IOMMU_HWPT_ALLOC_IOPF_CAPABLE flag when allocating a > > > hardware page table (HWPT). IOMMUFD will then set up its infrastructure > > > for page fault delivery. On a successful return of HWPT allocation, the > > > user can retrieve and respond to page faults by reading and writing to > > > the file descriptor (FD) returned in out_fault_fd. > > > > This is probably backwards, userspace should allocate the FD with a > > dedicated ioctl and provide it during domain allocation. > > Introducing a dedicated fault FD for fault handling seems promising. It > decouples the fault handling from any specific domain. I suppose we need > different fault fd for recoverable faults (a.k.a. IO page fault) and > unrecoverable faults. Do I understand you correctly? I haven't thought that far ahead :) Once you have a generic fault FD concept it can be sliced in different ways. If there is a technical need to seperate recoverable/unrecoverable then the FD flavour should be specified during FD creation. Otherwise just let userspace do whatever it wants. Jason
