I'm wondering if resetting the IOMMU at init-time (once) would clear any BIOS induced noise. Leo
> -----Original Message----- > From: iommu-boun...@lists.linux-foundation.org [mailto:iommu- > boun...@lists.linux-foundation.org] On Behalf Of Don Dutile > Sent: Monday, April 29, 2013 3:10 PM > To: Suthikulpanit, Suravee > Cc: io...@lists.linux-foundation.org; linux-kernel@vger.kernel.org > Subject: Re: RFC: IOMMU/AMD: Error Handling > > On 04/29/2013 03:45 PM, Suravee Suthikulanit wrote: > > Joerg, > > > > 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: > > - DEV_TAB_HADWARE_ERROR > > - PAGE_TAB_ERROR > > - COMMAND_HARDWARE_ERROR > > 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: > > - ILLEGAL_DEV_TABLE_ENTRY > > - IO_PAGE_FAULT > > - INVALDE_DEVICE_REQUEST > > 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. > > > disabling the device is not an option. > We've seen mis-configured ACPI tables generate storms of invalide dte > messages after iommu setup but before they are cleared up when the OS > driver is started & resets the device. The original storm is from bios-use of > IOMMU with a device. > I'd recommend creating a filter that prevents further logging from a device > for 5 mins at a time if a storm of DTE-related errors are seen. > by definition, the DMA is blocked from corrupting/changing memory, so > isolation has been established; keeping the failure log from consuming the > system is the needed fix. > > > 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? > > > Wondering if you could use AER-like callback mechanism so a driver can be > invoked when IOMMU error occurs, so the device driver can quiesce or reset > the device if it deems it transient. > > > > Any feedback or comments are appreciated. > > > > Thank you, > > Suravee > > > > > > > > > > _______________________________________________ > > iommu mailing list > > io...@lists.linux-foundation.org > > https://lists.linuxfoundation.org/mailman/listinfo/iommu > > _______________________________________________ > iommu mailing list > io...@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/iommu -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
