RFC: IOMMU/AMD: Error Handling
From: Suravee Suthikulanit
Date: Mon Apr 29 2013 - 15:45:53 EST
We are in the process of implementing AMD IOMMU error handling, and I
would like some comments from you and the community.
Currently, the AMD IOMMU driver only reports events from the event log
in the dmesg, and does not try to handle them in case of errors. AMD
IOMMU errors can be categorized as device-specific errors and IOMMU errors.
1. For IOMMU errors such as:
If the error is detected during IOMMU initialization, we could disable
IOMMU and proceed. If the error occurs after IOMMU is initialized, we
won't be able to recover from this, and might need to result in panic.
2. For device-specific errors such as:
We think the AMD IOMMU driver should try to isolate the device. This
involves blocking device transactions at IOMMU DTE and tries to disable
the device (e.g. calling the remove(struct pci_dev *pdev) interface
generally provides by device drivers). This could prevents the device
from continuing to fail and to risk of system instability.
3. In case of posted memory write transaction, device driver might not
be aware that the transaction has failed and blocked at IOMMU. If there
is no HW IOMMU, I believe this is handled by PCI error handling code.
If the IOMMU hardware reporth such case, could this potentially leverage
the Linux IOMMU fault handling interface, iommu_set_fault_handler() and
report_iommu_fault(), to communicate to device driver or PCI driver?
Any feedback or comments are appreciated.
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