Messages in this thread | | | Date | Mon, 29 Apr 2013 17:42:24 -0400 | From | Don Dutile <> | Subject | Re: RFC: IOMMU/AMD: Error Handling |
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On 04/29/2013 04:34 PM, Duran, Leo wrote: > I'm wondering if resetting the IOMMU at init-time (once) would clear any BIOS induced noise. > Leo > Well, depends what you mean by 'reset'.... (a) setting it up for OS use is effectively a reset, but doesn't quiesce a device doing dma reads of a (bios-setup) queue. then the noisy messages begin (b) disable the iommu, and then the dma just occurs... and bad for writes, potentially.
Similar issue is being reported & worked for kdump, where device are still doing DMA while the system is trying to 'reset' to the kexec'd kernel, and take a crash dump.
Solution: stop devices from doing dma... but some you _want_ enabled throughout... like keyboard & mouse via usb controller, so you get to pick os from grub... not so for kexec...
so, again, for isolation faults.... let the hw do its job -- isolate and throttle/silence the fault messages on a per-device, time-duration heuristic so the system can get through boot-up where enough OS is init'd (drivers started) to stop the temporary noise.
>> -----Original Message----- >> From: iommu-bounces@lists.linux-foundation.org [mailto:iommu- >> bounces@lists.linux-foundation.org] On Behalf Of Don Dutile >> Sent: Monday, April 29, 2013 3:10 PM >> To: Suthikulpanit, Suravee >> Cc: iommu@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 >>> iommu@lists.linux-foundation.org >>> https://lists.linuxfoundation.org/mailman/listinfo/iommu >> >> _______________________________________________ >> iommu mailing list >> iommu@lists.linux-foundation.org >> https://lists.linuxfoundation.org/mailman/listinfo/iommu > >
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