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 E8730C3063E for ; Thu, 17 Aug 2023 15:19:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353097AbjHQPSe (ORCPT ); Thu, 17 Aug 2023 11:18:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42952 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353120AbjHQPS3 (ORCPT ); Thu, 17 Aug 2023 11:18:29 -0400 Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.31]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 28B3B1AE; Thu, 17 Aug 2023 08:18:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1692285506; x=1723821506; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=QMgQfXBYJt0EBpimhe5IYAhnYAqWB+WrvTqlDZfpL3w=; b=FOLHCzY3pqHfPw2gmRK+O3Lzov+/8YKK3aZ/6R9TCqoWH8bQ478XQ+Uz HeYOWsogLVCVdw3tRKI1XeKK0h7LeHL/hPFkHmNfRxxwp0dzxbOynEAbA zNsIdXg+zepLcmOEy7DQourD1ju7VsbZFwu8Q1DaPHoU/Z5MWjZahW6BJ e+xlnCPRPIVKxaw7txxLWIENZvXb4R5At6JyF/eZsxdEbPnTpcyXoocXQ q/OOzuZWxZItscNvI8mAdv7xH2wNjfjrISQBrAF8CKW8XxrUjqXnyqyaB VzpS5w2vcY0LQmEpgeKtqN9nM69rqbtqwzVybq0zgfAFKRc2yasiKdZu5 Q==; X-IronPort-AV: E=McAfee;i="6600,9927,10805"; a="436756642" X-IronPort-AV: E=Sophos;i="6.01,180,1684825200"; d="scan'208";a="436756642" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Aug 2023 08:18:17 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10805"; a="684448527" X-IronPort-AV: E=Sophos;i="6.01,180,1684825200"; d="scan'208";a="684448527" Received: from kaeanliu-mobl.amr.corp.intel.com (HELO himmelriiki) ([10.252.52.225]) by orsmga003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Aug 2023 08:18:10 -0700 Date: Thu, 17 Aug 2023 18:18:06 +0300 From: Mikko Ylinen To: Haitao Huang Cc: 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 , 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 Subject: Re: [PATCH v3 22/28] Docs/x86/sgx: Add description for cgroup support Message-ID: References: <20230712230202.47929-1-haitao.huang@linux.intel.com> <20230712230202.47929-23-haitao.huang@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230712230202.47929-23-haitao.huang@linux.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org On Wed, Jul 12, 2023 at 04:01:56PM -0700, 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. Document the behavior when reclaim cannot happen, e.g., for the vEPC pages when a VMM tries to allocate more than misc.max. > + > + 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. > -- > 2.25.1 >