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[180.214.232.13]) by smtp.gmail.com with ESMTPSA id s11-20020a17090a13cb00b002071ee97923sm6081582pjf.53.2022.11.12.01.28.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 12 Nov 2022 01:28:38 -0800 (PST) Message-ID: <483efb64-4c8f-7b0e-059c-b2421a9e33b5@gmail.com> Date: Sat, 12 Nov 2022 16:28:32 +0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.1 Subject: Re: [PATCH 26/26] Docs/x86/sgx: Add description for cgroup support To: Kristen Carlson Accardi , jarkko@kernel.org, dave.hansen@linux.kernel.org, tj@kernel.org, linux-kernel@vger.kernel.org, linux-sgx@vger.kernel.org, cgroups@vger.kernel.org, Dave Hansen , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Jonathan Corbet Cc: zhiquan1.li@intel.com, Sean Christopherson , linux-doc@vger.kernel.org References: <20221111183532.3676646-1-kristen@linux.intel.com> <20221111183532.3676646-27-kristen@linux.intel.com> Content-Language: en-US From: Bagas Sanjaya In-Reply-To: <20221111183532.3676646-27-kristen@linux.intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 11/12/22 01:35, Kristen Carlson Accardi wrote: > diff --git a/Documentation/x86/sgx.rst b/Documentation/x86/sgx.rst > index 2bcbffacbed5..f6ca5594dcf2 100644 > --- a/Documentation/x86/sgx.rst > +++ b/Documentation/x86/sgx.rst > @@ -300,3 +300,80 @@ 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 subsytem, 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 EPC cannot be reclaimed in > + a timely manner, reclaim will be forced, e.g. by ignoring LRU. > + > + misc.events > + A read-write flat-keyed file which exists on non-root cgroups. > + Writes to the file reset the event counters to zero. 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. The doc LGTM, thanks. Reviewed-by: Bagas Sanjaya -- An old man doll... just what I always wanted! - Clara