On Mon, 2019-06-17 at 12:12 -0700, Andy Lutomirski wrote:
> On Mon, Jun 17, 2019 at 11:37 AM Dave Hansen <dave.hansen@xxxxxxxxx> wrote:
> >
> > Tom Lendacky, could you take a look down in the message to the talk of
> > SEV? I want to make sure I'm not misrepresenting what it does today.
> > ...
> >
> >
> > > > I actually don't care all that much which one we end up with. It's not
> > > > like the extra syscall in the second options means much.
> > >
> > > The benefit of the second one is that, if sys_encrypt is absent, it
> > > just works. In the first model, programs need a fallback because
> > > they'll segfault of mprotect_encrypt() gets ENOSYS.
> >
> > Well, by the time they get here, they would have already had to allocate
> > and set up the encryption key. I don't think this would really be the
> > "normal" malloc() path, for instance.
> >
> > > > How do we
> > > > eventually stack it on top of persistent memory filesystems or Device
> > > > DAX?
> > >
> > > How do we stack anonymous memory on top of persistent memory or Device
> > > DAX? I'm confused.
> >
> > If our interface to MKTME is:
> >
> > fd = open("/dev/mktme");
> > ptr = mmap(fd);
> >
> > Then it's hard to combine with an interface which is:
> >
> > fd = open("/dev/dax123");
> > ptr = mmap(fd);
> >
> > Where if we have something like mprotect() (or madvise() or something
> > else taking pointer), we can just do:
> >
> > fd = open("/dev/anything987");
> > ptr = mmap(fd);
> > sys_encrypt(ptr);
>
> I'm having a hard time imagining that ever working -- wouldn't it blow
> up if someone did:
>
> fd = open("/dev/anything987");
> ptr1 = mmap(fd);
> ptr2 = mmap(fd);
> sys_encrypt(ptr1);
>
> So I think it really has to be:
> fd = open("/dev/anything987");
> ioctl(fd, ENCRYPT_ME);
> mmap(fd);
This requires "/dev/anything987" to support ENCRYPT_ME ioctl, right?
So to support NVDIMM (DAX), we need to add ENCRYPT_ME ioctl to DAX?
>
> But I really expect that the encryption of a DAX device will actually
> be a block device setting and won't look like this at all. It'll be
> more like dm-crypt except without device mapper.
Are you suggesting not to support MKTME for DAX, or adding MKTME support to dm-crypt?
Thanks,
-Kai
