From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ram Pai Subject: Re: [PATCH] x86, powerpc : pkey-mprotect must allow pkey-0 Date: Fri, 9 Mar 2018 21:55:44 -0800 Message-ID: <20180310055544.GU1060@ram.oc3035372033.ibm.com> References: <1520583161-11741-1-git-send-email-linuxram@us.ibm.com> <60886e4a-59d4-541a-a6af-d4504e6719ad@intel.com> Reply-To: Ram Pai Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <60886e4a-59d4-541a-a6af-d4504e6719ad@intel.com> Sender: linux-kernel-owner@vger.kernel.org To: Dave Hansen Cc: mpe@ellerman.id.au, mingo@redhat.com, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, x86@kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, benh@kernel.crashing.org, paulus@samba.org, khandual@linux.vnet.ibm.com, aneesh.kumar@linux.vnet.ibm.com, bsingharora@gmail.com, hbabu@us.ibm.com, mhocko@kernel.org, bauerman@linux.vnet.ibm.com, ebiederm@xmission.com, corbet@lwn.net, arnd@arndb.de, fweimer@redhat.com, msuchanek@suse.com, Ulrich.Weigand@de.ibm.com List-Id: linux-arch.vger.kernel.org On Fri, Mar 09, 2018 at 02:40:32PM -0800, Dave Hansen wrote: > On 03/09/2018 12:12 AM, Ram Pai wrote: > > Once an address range is associated with an allocated pkey, it cannot be > > reverted back to key-0. There is no valid reason for the above behavior. On > > the contrary applications need the ability to do so. > > Why don't we just set pkey 0 to be allocated in the allocation bitmap by > default? ok. that will make it allocatable. But it will not be associatable, given the bug in the current code. And what will be the default key associated with a pte? zero? or something else? > > We *could* also just not let it be special and let it be freed. An app > could theoretically be careful and make sure nothing is using it. unable to see how this solves the problem. Need some more explaination. RP From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:51342 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750858AbeCJF4A (ORCPT ); Sat, 10 Mar 2018 00:56:00 -0500 Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w2A5sq30006421 for ; Sat, 10 Mar 2018 00:56:00 -0500 Received: from e06smtp11.uk.ibm.com (e06smtp11.uk.ibm.com [195.75.94.107]) by mx0b-001b2d01.pphosted.com with ESMTP id 2gm31y1qqk-1 (version=TLSv1.2 cipher=AES256-SHA256 bits=256 verify=NOT) for ; Sat, 10 Mar 2018 00:55:59 -0500 Received: from localhost by e06smtp11.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sat, 10 Mar 2018 05:55:58 -0000 Date: Fri, 9 Mar 2018 21:55:44 -0800 From: Ram Pai Subject: Re: [PATCH] x86, powerpc : pkey-mprotect must allow pkey-0 Reply-To: Ram Pai References: <1520583161-11741-1-git-send-email-linuxram@us.ibm.com> <60886e4a-59d4-541a-a6af-d4504e6719ad@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <60886e4a-59d4-541a-a6af-d4504e6719ad@intel.com> Message-ID: <20180310055544.GU1060@ram.oc3035372033.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Dave Hansen Cc: mpe@ellerman.id.au, mingo@redhat.com, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, x86@kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, benh@kernel.crashing.org, paulus@samba.org, khandual@linux.vnet.ibm.com, aneesh.kumar@linux.vnet.ibm.com, bsingharora@gmail.com, hbabu@us.ibm.com, mhocko@kernel.org, bauerman@linux.vnet.ibm.com, ebiederm@xmission.com, corbet@lwn.net, arnd@arndb.de, fweimer@redhat.com, msuchanek@suse.com, Ulrich.Weigand@de.ibm.com Message-ID: <20180310055544.wzFrG6pg__1ihx0CJ8jv0MZmDdZkpB_yiPFZcSKk-Dk@z> On Fri, Mar 09, 2018 at 02:40:32PM -0800, Dave Hansen wrote: > On 03/09/2018 12:12 AM, Ram Pai wrote: > > Once an address range is associated with an allocated pkey, it cannot be > > reverted back to key-0. There is no valid reason for the above behavior. On > > the contrary applications need the ability to do so. > > Why don't we just set pkey 0 to be allocated in the allocation bitmap by > default? ok. that will make it allocatable. But it will not be associatable, given the bug in the current code. And what will be the default key associated with a pte? zero? or something else? > > We *could* also just not let it be special and let it be freed. An app > could theoretically be careful and make sure nothing is using it. unable to see how this solves the problem. Need some more explaination. RP