On Mon, Feb 12, 2018 at 04:48:23PM +0000, Dmitry Safonov wrote: > dmar_fault() reports/handles/cleans DMAR faults in a cycle one-by-one. > The nuisance is that it's set as a irq handler and runs with disabled > interrupts - which works OK if you have only a couple of DMAR faults, > but becomes a problem if your intel iommu has a plenty of mappings.
I don't think that a work-queue is the right solution here, it adds a long delay until the log is processed. During that delay, and with high fault rates the error log will overflow during that delay. Here is what I think you should do instead to fix the soft-lockups: First, unmask the fault reporting irq so that you will get subsequent irqs. Then: * For Primary Fault Reporting just cycle once through all supported fault recording registers. * For Advanced Fault Reporting, read start and end pointer of the log and process all entries. After that return from the fault handler and let the next irq handle additional faults that might have been recorded while the previous handler was running. And of course, ratelimiting the fault printouts is always a good idea. Regards, Joerg