I see... I suppose the trick is going to be how to 'filter' this non intended behavior (once, during OS boot). Thanks, Leo.
> -----Original Message----- > From: Don Dutile [mailto:ddut...@redhat.com] > Sent: Monday, April 29, 2013 4:42 PM > To: Duran, Leo > Cc: Suthikulpanit, Suravee; io...@lists.linux-foundation.org; linux- > ker...@vger.kernel.org > Subject: Re: RFC: IOMMU/AMD: Error Handling > > 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-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/
