On 04/05/15 at 09:54am, Baoquan He wrote: > 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. It does not convince me, we should do it right at the beginning instead of introduce something wrong. I wonder why the old dma can not be remap to a specific page in kdump kernel so that it will not corrupt more memory. But I may missed something, I will looking for old threads and catch up. Thanks Dave
