On 04/15/15 at 01:47pm, Li, ZhenHua wrote: > On 04/15/2015 08:57 AM, Dave Young wrote: > >Again, I think it is bad to use old page table, below issues need consider: > >1) make sure old page table are reliable across crash > >2) do not allow writing oldmem after crash > > > >Please correct me if I'm wrong, or if above is not doable I think I will vote for > >resetting pci bus. > > > >Thanks > >Dave > > > Hi Dave, > > When updating the context tables, we have to write their address to root > tables, this will cause writing to old mem. > > Resetting the pci bus has been discussed, please check this: > http://lists.infradead.org/pipermail/kexec/2014-October/012752.html > https://lkml.org/lkml/2014/10/21/890 I know one reason to use old pgtable is this looks better because it fixes the real problem, but it is not a good way if it introduce more problems because of it have to use oldmem. I will be glad if this is not a problem but I have not been convinced. OTOH, there's many types of iommu, intel, amd, a lot of other types. They need their own fixes, so it looks not that elegant. For pci reset, it is not perfect, but it has another advantage, the patch is simpler. The problem I see from the old discusssion is, reset bus in 2nd kernel is acceptable but it does not fix things on sparc platform. AFAIK current reported problems are intel and amd iommu, at least pci reset stuff does not make it worse. Thanks Dave
