Re: [PATCH, RFC 47/62] mm: Restrict MKTME memory encryption to anonymous VMAs

[Alison Schofield]

On Fri, Jun 14, 2019 at 01:55:20PM +0200, Peter Zijlstra wrote:
> On Wed, May 08, 2019 at 05:44:07PM +0300, Kirill A. Shutemov wrote:
> > From: Alison Schofield <alison.schofield@xxxxxxxxx>
> > 
> > Memory encryption is only supported for mappings that are ANONYMOUS.
> > Test the VMA's in an encrypt_mprotect() request to make sure they all
> > meet that requirement before encrypting any.
> > 
> > The encrypt_mprotect syscall will return -EINVAL and will not encrypt
> > any VMA's if this check fails.
> > 
> > Signed-off-by: Alison Schofield <alison.schofield@xxxxxxxxx>
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> 
> This should be folded back into the initial implemention, methinks.

It is part of the initial implementation. I looked for
places to split the implementation into smaller,
reviewable patches, hence this split. None of it gets
built until the CONFIG_X86_INTEL_MKTME is introduced
in a later patch.

The encrypt_mprotect() patchset is ordered like this:
1) generalize mprotect to support the mktme extension
2) wire up encrypt_mprotect()
3) implement encrypt_mprotect()
4) keep reference counts on encryption keys (was VMAs)
5) (this patch) restrict to anonymous VMAs.
  
I thought Patch 5) was a small, but meaningful split. It 
accentuates the fact that MKTME is restricted to anonymous
memory.

Alas, I want to make it logical to review, so I'll move it.