[Patch v5 2/2] cgroup: svm: Encryption IDs cgroup documentation.

[Vipin Sharma]

Documentation of Encryption IDs controller. This new controller is used
to track and limit usage of hardware memory encryption capabilities on
the CPUs.

Signed-off-by: Vipin Sharma <vipinsh@xxxxxxxxxx>
Reviewed-by: David Rientjes <rientjes@xxxxxxxxxx>
Reviewed-by: Dionna Glaze <dionnaglaze@xxxxxxxxxx>
---
 .../admin-guide/cgroup-v1/encryption_ids.rst  |  1 +
 Documentation/admin-guide/cgroup-v2.rst       | 78 ++++++++++++++++++-
 2 files changed, 77 insertions(+), 2 deletions(-)
 create mode 100644 Documentation/admin-guide/cgroup-v1/encryption_ids.rst

diff --git a/Documentation/admin-guide/cgroup-v1/encryption_ids.rst b/Documentation/admin-guide/cgroup-v1/encryption_ids.rst
new file mode 100644
index 000000000000..8e9e9311daeb
--- /dev/null
+++ b/Documentation/admin-guide/cgroup-v1/encryption_ids.rst
@@ -0,0 +1 @@
+/Documentation/admin-guide/cgroup-v2.rst
diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 63521cd36ce5..72993571de2e 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -63,8 +63,11 @@ v1 is available under :ref:`Documentation/admin-guide/cgroup-v1/index.rst <cgrou
        5-7-1. RDMA Interface Files
      5-8. HugeTLB
        5.8-1. HugeTLB Interface Files
-     5-8. Misc
-       5-8-1. perf_event
+     5-9. Encryption IDs
+       5.9-1 Encryption IDs Interface Files
+       5.9-2 Migration and Ownership
+     5-10. Misc
+       5-10-1. perf_event
      5-N. Non-normative information
        5-N-1. CPU controller root cgroup process behaviour
        5-N-2. IO controller root cgroup process behaviour
@@ -2160,6 +2163,77 @@ HugeTLB Interface Files
 	are local to the cgroup i.e. not hierarchical. The file modified event
 	generated on this file reflects only the local events.
 
+Encryption IDs
+--------------
+
+There are multiple hardware memory encryption capabilities provided by the
+hardware vendors, like Secure Encrypted Virtualization (SEV) and SEV Encrypted
+State (SEV-ES) from AMD.
+
+These features are being used in encrypting virtual machines (VMs) and user
+space programs. However, only a small number of keys/IDs can be used
+simultaneously.
+
+This limited availability of these IDs requires system admin to optimize
+allocation, control, and track the usage of the resources in the cloud
+infrastructure. This resource also needs to be protected from getting exhausted
+by some malicious program and causing starvation for other programs.
+
+Encryption IDs controller provides capability to register the resource for
+controlling and tracking through the cgroups.
+
+Encryption IDs Interface Files
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Each encryption ID type have their own interface files,
+encids.[ID TYPE].{max, current, stat}, where "ID TYPE" can be sev and
+sev-es.
+
+  encids.[ID TYPE].stat
+        A read-only flat-keyed single value file. This file exists only in the
+        root cgroup.
+
+        It shows the total number of encryption IDs available and currently in
+        use on the platform::
+          # cat encids.sev.stat
+          total 509
+          used 0
+
+  encids.[ID TYPE].max
+        A read-write file which exists on the non-root cgroups. File is used to
+        set maximum count of "[ID TYPE]" which can be used in the cgroup.
+
+        Limit can be set to max by::
+          # echo max > encids.sev.max
+
+        Limit can be set by::
+          # echo 100 > encids.sev.max
+
+        This file shows the max limit of the encryption ID in the cgroup::
+          # cat encids.sev.max
+          max
+
+        OR::
+          # cat encids.sev.max
+          100
+
+        Limits can be set more than the "total" capacity value in the
+        encids.[ID TYPE].stat file, however, the controller ensures
+        that the usage never exceeds the "total" and the max limit.
+
+  encids.[ID TYPE].current
+        A read-only single value file which exists on non-root cgroups.
+
+        Shows the total number of encrypted IDs being used in the cgroup.
+
+Migration and Ownership
+~~~~~~~~~~~~~~~~~~~~~~~
+
+An encryption ID is charged to the cgroup in which it is used first, and
+stays charged to that cgroup until that ID is freed. Migrating a process
+to a different cgroup do not move the charge to the destination cgroup
+where the process has moved.
+
 Misc
 ----
 
-- 
2.30.0.284.gd98b1dd5eaa7-goog