iommu: introduce device fault report API
hulk inclusion category: feature bugzilla: 14369 CVE: NA ------------------- Traditionally, device specific faults are detected and handled within their own device drivers. When IOMMU is enabled, faults such as DMA related transactions are detected by IOMMU. There is no generic reporting mechanism to report faults back to the in-kernel device driver or the guest OS in case of assigned devices. Faults detected by IOMMU is based on the transaction's source ID which can be reported at per device basis, regardless of the device type is a PCI device or not. The fault types include recoverable (e.g. page request) and unrecoverable faults(e.g. access error). In most cases, faults can be handled by IOMMU drivers internally. The primary use cases are as follows: 1. page request fault originated from an SVM capable device that is assigned to guest via vIOMMU. In this case, the first level page tables are owned by the guest. Page request must be propagated to the guest to let guest OS fault in the pages then send page response. In this mechanism, the direct receiver of IOMMU fault notification is VFIO, which can relay notification events to QEMU or other user space software. 2. faults need more subtle handling by device drivers. Other than simply invoke reset function, there are needs to let device driver handle the fault with a smaller impact. This patchset is intended to create a generic fault report API such that it can scale as follows: - all IOMMU types - PCI and non-PCI devices - recoverable and unrecoverable faults - VFIO and other other in kernel users - DMA & IRQ remapping (TBD) The original idea was brought up by David Woodhouse and discussions summarized at https://lwn.net/Articles/608914/ . Signed-off-by:Jacob Pan <jacob.jun.pan@linux.intel.com> Signed-off-by:
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