[PATCHv2 57/59] x86/mktme: Document the MKTME Key Service API

Kirill A. Shutemov
2019-07-31T15:21:02Z

From: Alison Schofield <alison.schofield@intel.com>

Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
Documentation/x86/mktme/index.rst | 1 +
Documentation/x86/mktme/mktme_keys.rst | 61 ++++++++++++++++++++++++++
2 files changed, 62 insertions(+)
create mode 100644 Documentation/x86/mktme/mktme_keys.rst

diff --git a/Documentation/x86/mktme/index.rst b/Documentation/x86/mktme/index.rst
index 0f021cc4a2db..8cf2b7d62091 100644
--- a/Documentation/x86/mktme/index.rst
+++ b/Documentation/x86/mktme/index.rst
@@ -8,3 +8,4 @@ Multi-Key Total Memory Encryption (MKTME)
mktme_overview
mktme_mitigations
mktme_configuration
+ mktme_keys
diff --git a/Documentation/x86/mktme/mktme_keys.rst b/Documentation/x86/mktme/mktme_keys.rst
new file mode 100644
index 000000000000..5d9125eb7950
--- /dev/null
+++ b/Documentation/x86/mktme/mktme_keys.rst
@@ -0,0 +1,61 @@
+MKTME Key Service API
+=====================
+MKTME is a new key service type added to the Linux Kernel Key Service.
+
+The MKTME Key Service type is available when CONFIG_X86_INTEL_MKTME is
+turned on in Intel platforms that support the MKTME feature.
+
+The MKTME Key Service type manages the allocation of hardware encryption
+keys. Users can request an MKTME type key and then use that key to
+encrypt memory with the encrypt_mprotect() system call.
+
+Usage
+-----
+ When using the Kernel Key Service to request an *mktme* key,
+ specify the *payload* as follows:
+
+ type=
+ *cpu* User requests a CPU generated encryption key.
+ The CPU generates and assigns an ephemeral key.
+
+ *no-encrypt*
+ User requests that hardware does not encrypt
+ memory when this key is in use.
+
+ algorithm=
+ When type=cpu the algorithm field must be *aes-xts-128*
+ *aes-xts-128* is the only supported encryption algorithm
+
+ When type=no-encrypt the algorithm field must not be
+ present in the payload.
+
+ERRORS
+------
+ In addition to the Errors returned from the Kernel Key Service,
+ add_key(2) or keyctl(1) commands, the MKTME Key Service type may
+ return the following errors:
+
+ EINVAL for any payload specification that does not match the
+ MKTME type payload as defined above.
+
+ EACCES for access denied. The MKTME key type uses capabilities
+ to restrict the allocation of keys to privileged users.
+ CAP_SYS_RESOURCE is required, but it will accept the
+ broader capability of CAP_SYS_ADMIN. See capabilities(7).
+
+ ENOKEY if a hardware key cannot be allocated. Additional error
+ messages will describe the hardware programming errors.
+
+EXAMPLES
+--------
+ Add a 'cpu' type key::
+
+ char \*options_CPU = "type=cpu algorithm=aes-xts-128";
+
+ key = add_key("mktme", "name", options_CPU, strlen(options_CPU),
+ KEY_SPEC_THREAD_KEYRING);
+
+ Add a "no-encrypt' type key::
+
+ key = add_key("mktme", "name", "no-encrypt", strlen(options_CPU),
+ KEY_SPEC_THREAD_KEYRING);
--
2.21.0