Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752105AbbLHTG7 (ORCPT ); Tue, 8 Dec 2015 14:06:59 -0500 Received: from www.sr71.net ([198.145.64.142]:52180 "EHLO blackbird.sr71.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751960AbbLHTG5 (ORCPT ); Tue, 8 Dec 2015 14:06:57 -0500 Subject: Re: [PATCH 28/34] x86: wire up mprotect_key() system call To: Thomas Gleixner References: <20151204011424.8A36E365@viggo.jf.intel.com> <20151204011503.2A095839@viggo.jf.intel.com> Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, dave.hansen@linux.intel.com, linux-api@vger.kernel.org From: Dave Hansen Message-ID: <56672A50.4010801@sr71.net> Date: Tue, 8 Dec 2015 11:06:56 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1391 Lines: 32 On 12/08/2015 10:44 AM, Thomas Gleixner wrote: > On Thu, 3 Dec 2015, Dave Hansen wrote: >> #include >> diff -puN mm/Kconfig~pkeys-16-x86-mprotect_key mm/Kconfig >> --- a/mm/Kconfig~pkeys-16-x86-mprotect_key 2015-12-03 16:21:31.114920208 -0800 >> +++ b/mm/Kconfig 2015-12-03 16:21:31.119920435 -0800 >> @@ -679,4 +679,5 @@ config NR_PROTECTION_KEYS >> # Everything supports a _single_ key, so allow folks to >> # at least call APIs that take keys, but require that the >> # key be 0. >> + default 16 if X86_INTEL_MEMORY_PROTECTION_KEYS >> default 1 > > What happens if I set that to 42? > > I think we want to make this a runtime evaluated thingy. If pkeys are > compiled in, but the machine does not support it then we don't support > 16 keys, or do we? We do have runtime evaluation: #define arch_max_pkey() (boot_cpu_has(X86_FEATURE_OSPKE) ? \ CONFIG_NR_PROTECTION_KEYS : 1) The config option really just sets the architectural limit for how many are supported. So it probably needs a better name at least. Let me take a look at getting rid of this config option entirely. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/