@@ -300,3 +300,77 @@ to expected failures and handle them as follows:
first call. It indicates a bug in the kernel or the userspace client
if any of the second round of ``SGX_IOC_VEPC_REMOVE_ALL`` calls has
a return code other than 0.
+
+
+Cgroup Support
+==============
+
+The "sgx_epc" resource within the Miscellaneous cgroup controller regulates distribution of SGX
+EPC memory, which is a subset of system RAM that is used to provide SGX-enabled applications
+with protected memory, and is otherwise inaccessible, i.e. shows up as reserved in /proc/iomem
+and cannot be read/written outside of an SGX enclave.
+
+Although current systems implement EPC by stealing memory from RAM, for all intents and
+purposes the EPC is independent from normal system memory, e.g. must be reserved at boot from
+RAM and cannot be converted between EPC and normal memory while the system is running. The EPC
+is managed by the SGX subsystem and is not accounted by the memory controller. Note that this
+is true only for EPC memory itself, i.e. normal memory allocations related to SGX and EPC
+memory, e.g. the backing memory for evicted EPC pages, are accounted, limited and protected by
+the memory controller.
+
+Much like normal system memory, EPC memory can be overcommitted via virtual memory techniques
+and pages can be swapped out of the EPC to their backing store (normal system memory allocated
+via shmem). The SGX EPC subsystem is analogous to the memory subsystem, and it implements
+limit and protection models for EPC memory.
+
+SGX EPC Interface Files
+-----------------------
+
+For a generic description of the Miscellaneous controller interface files, please see
+Documentation/admin-guide/cgroup-v2.rst
+
+All SGX EPC memory amounts are in bytes unless explicitly stated otherwise. If a value which
+is not PAGE_SIZE aligned is written, the actual value used by the controller will be rounded
+down to the closest PAGE_SIZE multiple.
+
+ misc.capacity
+ A read-only flat-keyed file shown only in the root cgroup. The sgx_epc resource will
+ show the total amount of EPC memory available on the platform.
+
+ misc.current
+ A read-only flat-keyed file shown in the non-root cgroups. The sgx_epc resource will
+ show the current active EPC memory usage of the cgroup and its descendants. EPC pages
+ that are swapped out to backing RAM are not included in the current count.
+
+ misc.max
+ A read-write single value file which exists on non-root cgroups. The sgx_epc resource
+ will show the EPC usage hard limit. The default is "max".
+
+ If a cgroup's EPC usage reaches this limit, EPC allocations, e.g. for page fault
+ handling, will be blocked until EPC can be reclaimed from the cgroup. If there are no
+ pages left that are reclaimable within the same group, the kernel returns ENOMEM.
+
+ The EPC pages allocated for a guest VM by the virtual EPC driver are not reclaimable by
+ the host kernel. In case the guest cgroup's limit is reached and no reclaimable pages
+ left in the same cgroup, the virtual EPC driver returns SIGBUS to the user space
+ process to indicate failure on new EPC allocation requests.
+
+ The misc.max limit is non-preemptive. If a user writes a limit lower than the current
+ usage to this file, the cgroup will not preemptively deallocate pages currently in use,
+ and will only start blocking the next allocation and reclaiming EPC at that time.
+
+ misc.events
+ A read-only flat-keyed file which exists on non-root cgroups.
+ A value change in this file generates a file modified event.
+
+ max
+ The number of times the cgroup has triggered a reclaim
+ due to its EPC usage approaching (or exceeding) its max
+ EPC boundary.
+
+Migration
+---------
+
+Once an EPC page is charged to a cgroup (during allocation), it remains charged to the original
+cgroup until the page is released or reclaimed. Migrating a process to a different cgroup
+doesn't move the EPC charges that it incurred while in the previous cgroup to its new cgroup.