From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756913AbdGLHjy (ORCPT ); Wed, 12 Jul 2017 03:39:54 -0400 Received: from mx2.suse.de ([195.135.220.15]:42072 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756657AbdGLHju (ORCPT ); Wed, 12 Jul 2017 03:39:50 -0400 Date: Wed, 12 Jul 2017 09:39:45 +0200 From: Michal Hocko To: Ram Pai Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, khandual@linux.vnet.ibm.com, aneesh.kumar@linux.vnet.ibm.com, bsingharora@gmail.com, dave.hansen@intel.com, hbabu@us.ibm.com, arnd@arndb.de, akpm@linux-foundation.org, corbet@lwn.net, mingo@redhat.com Subject: Re: [RFC v5 00/38] powerpc: Memory Protection Keys Message-ID: <20170712073945.GC28912@dhcp22.suse.cz> References: <1499289735-14220-1-git-send-email-linuxram@us.ibm.com> <20170711145246.GA11917@dhcp22.suse.cz> <20170711193257.GB5525@ram.oc3035372033.ibm.com> <20170712072337.GB28912@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170712072337.GB28912@dhcp22.suse.cz> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 12-07-17 09:23:37, Michal Hocko wrote: > On Tue 11-07-17 12:32:57, Ram Pai wrote: [...] > > Ideally the MMU looks at the PTE for keys, in order to enforce > > protection. This is the case with x86 and is the case with power9 Radix > > page table. Hence the keys have to be programmed into the PTE. > > But x86 doesn't update ptes for PKEYs, that would be just too expensive. > You could use standard mprotect to do the same... OK, this seems to be a misunderstanding and confusion on my end. do_mprotect_pkey does mprotect_fixup even for the pkey path which is quite surprising to me. I guess my misunderstanding comes from Documentation/x86/protection-keys.txt " Memory Protection Keys provides a mechanism for enforcing page-based protections, but without requiring modification of the page tables when an application changes protection domains. It works by dedicating 4 previously ignored bits in each page table entry to a "protection key", giving 16 possible keys. " So please disregard my previous comments about page tables and sorry about the confusion. -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [RFC v5 00/38] powerpc: Memory Protection Keys Date: Wed, 12 Jul 2017 09:39:45 +0200 Message-ID: <20170712073945.GC28912@dhcp22.suse.cz> References: <1499289735-14220-1-git-send-email-linuxram@us.ibm.com> <20170711145246.GA11917@dhcp22.suse.cz> <20170711193257.GB5525@ram.oc3035372033.ibm.com> <20170712072337.GB28912@dhcp22.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170712072337.GB28912@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org To: Ram Pai Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, khandual@linux.vnet.ibm.com, aneesh.kumar@linux.vnet.ibm.com, bsingharora@gmail.com, dave.hansen@intel.com, hbabu@us.ibm.com, arnd@arndb.de, akpm@linux-foundation.org, corbet@lwn.net, mingo@redhat.com List-Id: linux-arch.vger.kernel.org On Wed 12-07-17 09:23:37, Michal Hocko wrote: > On Tue 11-07-17 12:32:57, Ram Pai wrote: [...] > > Ideally the MMU looks at the PTE for keys, in order to enforce > > protection. This is the case with x86 and is the case with power9 Radix > > page table. Hence the keys have to be programmed into the PTE. > > But x86 doesn't update ptes for PKEYs, that would be just too expensive. > You could use standard mprotect to do the same... OK, this seems to be a misunderstanding and confusion on my end. do_mprotect_pkey does mprotect_fixup even for the pkey path which is quite surprising to me. I guess my misunderstanding comes from Documentation/x86/protection-keys.txt " Memory Protection Keys provides a mechanism for enforcing page-based protections, but without requiring modification of the page tables when an application changes protection domains. It works by dedicating 4 previously ignored bits in each page table entry to a "protection key", giving 16 possible keys. " So please disregard my previous comments about page tables and sorry about the confusion. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org