On Fri, 6 Oct 2017 10:36:02 +0100 Jean-Philippe Brucker <jean-philippe.bruc...@arm.com> wrote:
> Hi Jacob, > > On 06/10/17 00:03, Jacob Pan wrote: > > 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....@linux.intel.com> > > Signed-off-by: Ashok Raj <ashok....@intel.com> > > --- > [...] > > +int iommu_register_device_fault_handler(struct device *dev, > > + iommu_dev_fault_handler_t > > handler) +{ > > + if (dev->iommu_fault_param) > > + return -EBUSY; > > + get_device(dev); > > + dev->iommu_fault_param = > > + kzalloc(sizeof(struct iommu_fault_param), > > GFP_KERNEL); > > + if (!dev->iommu_fault_param) > > + return -ENOMEM; > > + dev->iommu_fault_param->dev_fault_handler = handler; > > Since the handler is owned by a device driver, you also need to clean > it up when switching the driver (native->VFIO and VFIO->native), in > iommu_attach_device I suppose. > I was thinking the driver who registered fault handler shall be held accountable to unregister. e.g. User must unbind driver (unregister fault handler included) before assigning device to vfio-pci. Otherwise, VFIO call to register handler would fail. I am assuming VFIO needs to have a separate device fault handler of its own. Jacob _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
