From patchwork Wed Sep 13 04:06:34 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Haitao Huang X-Patchwork-Id: 13382456 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 6A889EEB590 for ; Wed, 13 Sep 2023 04:09:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238479AbjIMEJq (ORCPT ); Wed, 13 Sep 2023 00:09:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56228 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238384AbjIMEJK (ORCPT ); Wed, 13 Sep 2023 00:09:10 -0400 Received: from mgamail.intel.com (mgamail.intel.com [192.55.52.136]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B656D19A7; Tue, 12 Sep 2023 21:09:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1694578140; x=1726114140; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=hEu3sY0L0Zm8yUMNRt51Y+KGZj58gXXJpRMwbPXfe14=; b=gaqSnY94y3UF2pguqjfrkbYW5gdGM8xzqQbZFSOGj65LIVAJpmBpZgxA u06VPICdNuNON9OBvhyD32NIOePuqpf1TVpvHJ6PfAqdFt1J9G8Zvt/H1 QMGBDU6D5MXdsq6tBfpYrdk2ySg7KNGqVm9bk4UO0aTvEU8XYC1El9P8H FCkyPaRlwWjCZtF7gB1QvMqzT7PlDJrtSbRVe0zpYeqlxl+6NxvcWSZ+R IyDlTLMd/yhpn5LTolwJTuc6+BX+WkRvSDy8rgnO3i1Thze04pWDU7mNJ jGx9Q6BJeGxuHUfSvtc4yAZ3vu6VUtRMMTsRBIpp2lNJlBZd66RGHviVL A==; X-IronPort-AV: E=McAfee;i="6600,9927,10831"; a="357990518" X-IronPort-AV: E=Sophos;i="6.02,142,1688454000"; d="scan'208";a="357990518" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Sep 2023 21:06:56 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10831"; a="747156017" X-IronPort-AV: E=Sophos;i="6.02,142,1688454000"; d="scan'208";a="747156017" Received: from b4969161e530.jf.intel.com ([10.165.56.46]) by fmsmga007.fm.intel.com with ESMTP; 12 Sep 2023 21:06:54 -0700 From: Haitao Huang To: jarkko@kernel.org, dave.hansen@linux.intel.com, tj@kernel.org, linux-kernel@vger.kernel.org, linux-sgx@vger.kernel.org, x86@kernel.org, cgroups@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, sohil.mehta@intel.com Cc: zhiquan1.li@intel.com, kristen@linux.intel.com, seanjc@google.com, zhanb@microsoft.com, anakrish@microsoft.com, mikko.ylinen@linux.intel.com, yangjie@microsoft.com Subject: [PATCH v4 17/18] Docs/x86/sgx: Add description for cgroup support Date: Tue, 12 Sep 2023 21:06:34 -0700 Message-Id: <20230913040635.28815-18-haitao.huang@linux.intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230913040635.28815-1-haitao.huang@linux.intel.com> References: <20230913040635.28815-1-haitao.huang@linux.intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org 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 Signed-off-by: Haitao Huang Cc: Sean Christopherson Reviewed-by: Bagas Sanjaya --- V4: - Fix indentation (Randy) - Change misc.events file to be read-only - Fix a typo for 'subsystem' - Add behavior when VMM overcommit EPC with a cgroup (Mikko) --- Documentation/arch/x86/sgx.rst | 82 ++++++++++++++++++++++++++++++++++ 1 file changed, 82 insertions(+) diff --git a/Documentation/arch/x86/sgx.rst b/Documentation/arch/x86/sgx.rst index d90796adc2ec..65c211bd5342 100644 --- a/Documentation/arch/x86/sgx.rst +++ b/Documentation/arch/x86/sgx.rst @@ -300,3 +300,85 @@ 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 EPC cannot be reclaimed in + a timely manner, reclaim will be forced, e.g. by ignoring LRU. + + The EPC pages allocated for KVM guests by the virtual EPC driver + are not reclaimable by the host kernel SGX reclaimers. If a VMM + tries to start a VM within a cgroup whose EPC usage reaches this + limit, the virtual EPC driver will stop allocating more EPC for the + VM, and return SIGBUS to the VMM which would abort the VM launch. + + 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.