On 04/03/15 at 05:21pm, Dave Young wrote: > On 04/03/15 at 05:01pm, Li, ZhenHua wrote: > > Hi Dave, > > > > There may be some possibilities that the old iommu data is corrupted by > > some other modules. Currently we do not have a better solution for the > > dmar faults. > > > > But I think when this happens, we need to fix the module that corrupted > > the old iommu data. I once met a similar problem in normal kernel, the > > queue used by the qi_* functions was written again by another module. > > The fix was in that module, not in iommu module. > > It is too late, there will be no chance to save vmcore then. > > Also if it is possible to continue corrupt other area of oldmem because > of using old iommu tables then it will cause more problems. > > So I think the tables at least need some verifycation before being used. > Yes, it's a good thinking anout this and verification is also an interesting idea. kexec/kdump do a sha256 calculation on loaded kernel and then verify this again when panic happens in purgatory. This checks whether any code stomps into region reserved for kexec/kernel and corrupt the loaded kernel. If this is decided to do it should be an enhancement to current patchset but not a approach change. Since this patchset is going very close to point as maintainers expected maybe this can be merged firstly, then think about enhancement. After all without this patchset vt-d often raised error message, hung. By the way I tested this patchset it works very well on my HP z420 work station. Thanks Baoquan
