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 X-Spam-Level: X-Spam-Status: No, score=-10.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 00328C4338F for ; Fri, 30 Jul 2021 20:35:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D132660F5E for ; Fri, 30 Jul 2021 20:35:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231444AbhG3Uf5 (ORCPT ); Fri, 30 Jul 2021 16:35:57 -0400 Received: from mga17.intel.com ([192.55.52.151]:49561 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231463AbhG3Ufw (ORCPT ); Fri, 30 Jul 2021 16:35:52 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10061"; a="193444416" X-IronPort-AV: E=Sophos;i="5.84,282,1620716400"; d="scan'208";a="193444416" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Jul 2021 13:35:45 -0700 X-IronPort-AV: E=Sophos;i="5.84,282,1620716400"; d="scan'208";a="477165440" Received: from cwschule-mobl.amr.corp.intel.com (HELO [10.212.156.26]) ([10.212.156.26]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Jul 2021 13:35:45 -0700 Subject: Re: [PATCH v3 2/7] x86/sgx: Add infrastructure to identify SGX EPC pages To: "Luck, Tony" Cc: Sean Christopherson , Jarkko Sakkinen , x86@kernel.org, linux-kernel@vger.kernel.org, Matthew Wilcox References: <20210719182009.1409895-1-tony.luck@intel.com> <20210728204653.1509010-1-tony.luck@intel.com> <20210728204653.1509010-3-tony.luck@intel.com> <141602a3-ef61-01f0-4a3c-69f8e7012fcd@intel.com> <20210730003809.hp3nmqmgyysa45nz@kernel.org> <20210730184400.GA1521057@agluck-desk2.amr.corp.intel.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210730184400.GA1521057@agluck-desk2.amr.corp.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/30/21 11:44 AM, Luck, Tony wrote: > @@ -649,6 +650,9 @@ static bool __init sgx_setup_epc_section(u64 phys_addr, u64 size, > } > > section->phys_addr = phys_addr; > + section->end_phys_addr = phys_addr + size - 1; > + xa_store_range(&epc_page_ranges, section->phys_addr, > + section->end_phys_addr, section, GFP_KERNEL); That is compact, but how much memory does it eat? I'm a little worried about this hunk of xa_store_range(): > do { > xas_set_range(&xas, first, last); > xas_store(&xas, entry); > if (xas_error(&xas)) > goto unlock; > first += xas_size(&xas); > } while (first <= last); That makes it look like it's iterating over the whole range and making loads of individual array instead of doing something super clever like keeping an extent-style structure. Let's say we have 1TB of EPC. How big is the array to store these indexes? Would this be more compact if instead of doing a physical address range: xa_store_range(&epc_page_ranges, section->phys_addr, section->end_phys_addr, ...); ... you did it based on PFNs: xa_store_range(&epc_page_ranges, section->phys_addr >> PAGE_SHIFT, section->end_phys_addr >> PAGE_SHIFT, ...); SGX sections are at *least* page-aligned, so this should be fine.