Hi, On 05/02/2018 08:38 PM, Dmitry Safonov wrote: > Hi Lu, > > On Wed, 2018-05-02 at 14:34 +0800, Lu Baolu wrote: >> Hi, >> >> On 03/31/2018 08:33 AM, Dmitry Safonov wrote: >>> Theoretically, on some machines faults might be generated faster >>> than >>> they're cleared by CPU. >> Is this a real case? > No. 1/2 is a real case and this one was discussed on v3: > lkml.kernel.org/r/<20180215191729.15777-1-d...@arista.com> > > It's not possible on my hw as far as I tried, but the discussion result > was to fix this theoretical issue too.
If faults are generated faster than CPU can clear them, the PCIe device should be in a very very bad state. How about disabling the PCIe device and ask the administrator to replace it? Anyway, I don't think that's goal of this patch series. :-) > >>> Let's limit the cleaning-loop by number of hw >>> fault registers. >> Will this cause the fault recording registers full of faults, hence >> new faults will be dropped without logging? > If faults come faster then they're being cleared - some of them will be > dropped without logging. Not sure if it's worth to report all faults in > such theoretical(!) situation. > If amount of reported faults for such situation is not enough and it's > worth to keep all the faults, then probably we should introduce a > workqueue here (which I did in v1, but it was rejected by the reason > that it will introduce some latency in fault reporting). > >> And even worse, new faults will not generate interrupts? > They will, we clear page fault overflow outside of the loop, so any new > fault will raise interrupt, iiuc. > I am afraid that they might not generate interrupts any more. Say, the fault registers are full of events that are not cleared, then a new fault comes. There is no room for this event and hence the hardware might drop it silently. Best regards, Lu Baolu _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
