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

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Date:   Tue, 19 Jan 2021 09:45:12 -0800
From:   Vipin Sharma <vipinsh@...gle.com>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Tom Lendacky <thomas.lendacky@....com>,
        Brijesh <brijesh.singh@....com>, Jon <jon.grimm@....com>,
        Eric <eric.vantassell@....com>, pbonzini@...hat.com,
        Sean Christopherson <seanjc@...gle.com>,
        Tejun Heo <tj@...nel.org>, hannes@...xchg.org,
        Janosch Frank <frankja@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>, corbet@....net,
        joro@...tes.org, vkuznets@...hat.com, wanpengli@...cent.com,
        Jim Mattson <jmattson@...gle.com>, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        Matt Gingell <gingell@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Dionna Glaze <dionnaglaze@...gle.com>, kvm@...r.kernel.org,
        x86@...nel.org, cgroups@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [Patch v5 2/2] cgroup: svm: Encryption IDs cgroup documentation.

On Mon, Jan 18, 2021 at 9:55 AM Randy Dunlap <rdunlap@...radead.org> wrote:
>
> 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@...gle.com>
> > Reviewed-by: David Rientjes <rientjes@...gle.com>
> > Reviewed-by: Dionna Glaze <dionnaglaze@...gle.com>
> > ---
> >  .../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

Thank you, I will fix them in the next patch.