On Sun, Jun 19, 2022 at 11:57:26PM -0300, Jason Gunthorpe wrote: > The remark about io memory is because on s390 memcpy() will crash even > on ioremapped memory, you have to use the memcpy_to/fromio() which > uses the special s390 io access instructions. Yes. The same is true for various other architectures, inluding arm64 under the right circumstances. > This helps because we now block io memory from ever getting into these > call paths. I'm pretty sure this is a serious security bug, but would > let the IBM folks remark as I don't know it all that well.. Prevent as in crash when trying to convert it to a page? > As for the kmap, I thought it was standard practice even if it is a > non-highmem? Aren't people trying to use this for other security > stuff these days? Ira has been lookin into the protection keys, although they don't apply to s390. Either way I don't object to using kmap, but the commit log doesn't make much sense to me.
