On Wed, Dec 05, 2018 at 10:11:18AM -0800, Andy Lutomirski wrote: > > > > On Dec 3, 2018, at 11:39 PM, Alison Schofield <alison.schofield@xxxxxxxxx> wrote: > > I realize you’re writing code to expose hardware behavior, but I’m not sure this > really makes sense in this context. Your observation is accurate. The Usage defined here is very closely aligned to the Intel MKTME Architecture spec. That's a starting point, but not the ending point. We need to implement the feature set that makes sense. More below... > > + > > + type= > > + *user* User will supply the encryption key data. Use this > > + type to directly program a hardware encryption key. > > + > > I think that “user” probably sense as a “key service” key, but I don’t think it is at all useful for non-persistent memory. Even if we take for granted that MKTME for anonymous memory is useful at all, “cpu” seems to be better in all respects. > > > Perhaps support for “user” should be tabled until there’s a design for how to use this for pmem? I imagine it would look quite a bit like dm-crypt. Advanced pmem filesystems could plausibly use different keys for different files, I suppose. > > If “user” is dropped, I think a lot of the complexity goes away. Hotplug becomes automatic, right? Dropping 'user' type removes a great deal of complexity. Let me follow up in 2 ways: 1) Find out when MKTME support for pmem is required. 2) Go back to the the requirements and get the justification for user type. > > > + *cpu* User requests a CPU generated encryption key. > > Okay, maybe, but it’s still unclear to me exactly what the intended benefit is, though. *cpu* is the RANDOM key generated by the cpu. If there were no other options, then this would be default, and go away. > > + *clear* User requests that a hardware encryption key be > > + cleared. This will clear the encryption key from > > + the hardware. On execution this hardware key gets > > + TME behavior. > > + > > Why is this a key type? Shouldn’t the API to select a key just have an option to ask for no key to be used? The *clear* key has been requested in order to clear/erase the users key data that has been programmed into a hardware slot. User does not want to leave a slot programmed with their encryption data when they are done with it. > > + *no-encrypt* > > + User requests that hardware does not encrypt > > + memory when this key is in use. > > Same as above. If there’s a performance benefit, then there could be a way to ask for cleartext memory. Similarly, some pmem users may want a way to keep their pmem unencrypted. So, this is the way to ask for cleartext memory. The entire system will be encrypted with the system wide TME Key. A subset of that will be protected with MKTME Keys. If user wants, no encrypt, this *no-encrypt* is the way to do it. Alison > > —Andy
