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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 3F6E4C04EB9 for ; Wed, 5 Dec 2018 05:41:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 043192081C for ; Wed, 5 Dec 2018 05:41:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 043192081C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-security-module-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726874AbeLEFlT (ORCPT ); Wed, 5 Dec 2018 00:41:19 -0500 Received: from mga14.intel.com ([192.55.52.115]:14725 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726768AbeLEFlT (ORCPT ); Wed, 5 Dec 2018 00:41:19 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Dec 2018 21:41:18 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,316,1539673200"; d="scan'208";a="123049832" Received: from alison-desk.jf.intel.com ([10.54.74.53]) by fmsmga002.fm.intel.com with ESMTP; 04 Dec 2018 21:41:18 -0800 Date: Tue, 4 Dec 2018 21:43:53 -0800 From: Alison Schofield To: Peter Zijlstra Cc: dhowells@redhat.com, tglx@linutronix.de, jmorris@namei.org, mingo@redhat.com, hpa@zytor.com, bp@alien8.de, luto@kernel.org, kirill.shutemov@linux.intel.com, dave.hansen@intel.com, kai.huang@intel.com, jun.nakajima@intel.com, dan.j.williams@intel.com, jarkko.sakkinen@intel.com, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org Subject: Re: [RFC v2 11/13] keys/mktme: Program memory encryption keys on a system wide basis Message-ID: <20181205054353.GE18596@alison-desk.jf.intel.com> References: <72dd5f38c1fdbc4c532f8caf2d2010f1ddfa8439.1543903910.git.alison.schofield@intel.com> <20181204092145.GR11614@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181204092145.GR11614@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Tue, Dec 04, 2018 at 10:21:45AM +0100, Peter Zijlstra wrote: > On Mon, Dec 03, 2018 at 11:39:58PM -0800, Alison Schofield wrote: > > > +static int mktme_build_leadcpus_mask(void) > > +{ > > + int online_cpu, mktme_cpu; > > + int online_pkgid, mktme_pkgid = -1; > > + > > + if (!zalloc_cpumask_var(&mktme_leadcpus, GFP_KERNEL)) > > + return -ENOMEM; > > + > > + for_each_online_cpu(online_cpu) { > > + online_pkgid = topology_physical_package_id(online_cpu); > > + > > + for_each_cpu(mktme_cpu, mktme_leadcpus) { > > + mktme_pkgid = topology_physical_package_id(mktme_cpu); > > + if (mktme_pkgid == online_pkgid) > > + break; > > + } > > + if (mktme_pkgid != online_pkgid) > > + cpumask_set_cpu(online_cpu, mktme_leadcpus); > > Do you really need LOCK prefixed bit set here? No. Changed to __cpumask_set_cpu(). Will check for other instances where I can skip LOCK prefix. > How is that serialized and kept relevant in the face of hotplug? mktme_leadcpus is updated on hotplug startup and teardowns. > Also, do you really need O(n^2) to find the first occurence of a value > in an array? How about this O(n)? unsigned long *pkg_map; int cpu, pkgid; if (!zalloc_cpumask_var(&mktme_leadcpus, GFP_KERNEL)) return -ENOMEM; pkg_map = bitmap_zalloc(topology_max_packages(), GFP_KERNEL); if (!pkg_map) { free_cpumask_var(mktme_leadcpus); return -ENOMEM; } for_each_online_cpu(cpu) { pkgid = topology_physical_package_id(cpu); if (!test_and_set_bit(pkgid, pkg_map)) __cpumask_set_cpu(cpu, mktme_leadcpus); }