From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A2C3EC001B0 for ; Thu, 13 Jul 2023 00:11:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232608AbjGMALG (ORCPT ); Wed, 12 Jul 2023 20:11:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34692 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230134AbjGMALE (ORCPT ); Wed, 12 Jul 2023 20:11:04 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 16B431FC8; Wed, 12 Jul 2023 17:11:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Sender:Reply-To:Content-ID:Content-Description; bh=9qXn+we4vl/6E7qv05qrX8iXxtrz7OQ9ZzhJSvff8Kc=; b=qhJaU/WRyim+49/LxqT2+QEPc+ pCd0GD9P1nk1zlaAiGQIJdpmTWnqLS6JONTSdB6dS0VfDtPp9k5BaINzFVn8l193BbZJJatf3CctK KtZdXK1UTgSdb3wvBtOzsUxCTP3ahqdZgcD4e0fsxMCwgfT91fQwh/NoQyXqDhwS7orJ9iVSBOywH i3oBsOjj87EMmIJKNrgplqkzn6zD6n1dgRID1iZUBuxH80nDjTIsEhZO2LUqCO4bnK/CSABkoRB7C tWq6Fxs3SMzzS/6X1CiroYvdabqNUux+ko99Pmu41c16vF0w9row/RLtadTFNHAcA4LUriAKL3tas COEHZi+g==; Received: from [2601:1c2:980:9ec0::2764] by bombadil.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1qJjvB-001YA3-0E; Thu, 13 Jul 2023 00:11:01 +0000 Message-ID: Date: Wed, 12 Jul 2023 17:10:59 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH v3 22/28] Docs/x86/sgx: Add description for cgroup support Content-Language: en-US To: Haitao Huang , jarkko@kernel.org, dave.hansen@linux.intel.com, tj@kernel.org, linux-kernel@vger.kernel.org, linux-sgx@vger.kernel.org, cgroups@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Jonathan Corbet Cc: kai.huang@intel.com, reinette.chatre@intel.com, Kristen Carlson Accardi , zhiquan1.li@intel.com, seanjc@google.com, bagasdotme@gmail.com, linux-doc@vger.kernel.org, zhanb@microsoft.com, anakrish@microsoft.com, mikko.ylinen@linux.intel.com References: <20230712230202.47929-1-haitao.huang@linux.intel.com> <20230712230202.47929-23-haitao.huang@linux.intel.com> From: Randy Dunlap In-Reply-To: <20230712230202.47929-23-haitao.huang@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 Hi, On 7/12/23 16:01, Haitao Huang wrote: > From: Kristen Carlson Accardi > > Add initial documentation of how to regulate the distribution of > SGX Enclave Page Cache (EPC) memory via the Miscellaneous cgroup > controller. > > Signed-off-by: Sean Christopherson > Signed-off-by: Kristen Carlson Accardi > Cc: Sean Christopherson > Reviewed-by: Bagas Sanjaya > --- > Documentation/arch/x86/sgx.rst | 77 ++++++++++++++++++++++++++++++++++ > 1 file changed, 77 insertions(+) > > diff --git a/Documentation/arch/x86/sgx.rst b/Documentation/arch/x86/sgx.rst > index 2bcbffacbed5..f6ca5594dcf2 100644 > --- a/Documentation/arch/x86/sgx.rst > +++ b/Documentation/arch/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. The indentation here (above) is a little confusing. Is this formatted the way that is intended? > + > +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. -- ~Randy