On Mon, 13 Nov 2017 13:19:50 +0000 Jean-Philippe Brucker <[email protected]> wrote:
> On 11/11/17 00:00, Jacob Pan wrote: > > On Fri, 10 Nov 2017 13:54:59 +0000 > > Jean-Philippe Brucker <[email protected]> wrote: > > > >> /* > >> * Note: I tried to synthesize what I believe would be useful to > >> device > >> * drivers and guests, with regards to the kind of faults that the > >> ARM > >> * SMMU is capable of reporting. Other IOMMUs may report more or > >> less > >> * fault reasons, and I guess one should try to associate the > >> faults > >> * reason that matches best a generic one when reporting a fault. > >> * > >> * Finer reason granularity is probably not useful to anyone, and > >> * coarser granularity would require more work from intermediate > >> * components processing the fault to figure out what happened, > >> whose > >> * fault it actually is and where to route it (process vs. device > >> driver > >> * vs. vIOMMU driver misprogamming tables). > >> */ > >> enum iommu_fault_reason { > >> IOMMU_FAULT_REASON_UNKNOWN = 0, > >> > > can we add one for iommu internal error, the specifics may not be > > useful for the device drivers, but it is good to know iommu is > > faulting, perhaps can take action that inform driver users. > > i.e. > > /* IOMMU internal error, no specific reason to report out */ > > IOMMU_FAULT_REASON_INTERNAL, > > Yes, and maybe it should replace IOMMU_FAULT_REASON_UNKNOWN, since the > device driver would probably handle it the same way. I guess the > INTERNAL fault is always fatal, meaning that the IOMMU is shutting > down and there is no hope to recover? I can't see a good reason to > inform users of non-fatal internal faults, the IOMMU driver will > print those to dmesg and keep going. For fatal faults we're telling > users to stop issuing transactions so the IOMMU driver doesn't get > flooded by events, for example. > Internal faults are not always fatal in vt-d, e.g. programming reserved bits, though it should fail in the first place when programming it synchronously as the code does today. I agree we put all internal faults under IOMMU_FAULT_REASON_INTERNAL, no more UNKNOWN, it is ambiguous in that unknown to device but known to iommu.
