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

[Randy Dunlap]

On 1/15/21 6:32 PM, Vipin Sharma wrote:
> 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

                                                          admins

> +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

   The Encryption IDs controller provides the capability to register the resource for

> +controlling and tracking through the cgroups.

                            through cgroups.

> +
> +Encryption IDs Interface Files
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +Each encryption ID type have their own interface files,

                           has its own

> +encids.[ID TYPE].{max, current, stat}, where "ID TYPE" can be sev and

                                                                     or

> +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

This is described above as a single-value file...

Is the max value a hardware limit or a software (flexible) limit?


> +
> +  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

                         does

> +where the process has moved.
> +
>  Misc
>  ----
>  
> 


-- 
~Randy
You can't do anything without having to do something else first.
-- Belefant's Law