From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f171.google.com (mail-pf0-f171.google.com [209.85.192.171]) by kanga.kvack.org (Postfix) with ESMTP id 05F7A6B0253 for ; Mon, 7 Mar 2016 16:34:24 -0500 (EST) Received: by mail-pf0-f171.google.com with SMTP id x188so62719294pfb.2 for ; Mon, 07 Mar 2016 13:34:23 -0800 (PST) Received: from aserp1040.oracle.com (aserp1040.oracle.com. [141.146.126.69]) by mx.google.com with ESMTPS id u64si31275909pfa.100.2016.03.07.13.34.22 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 07 Mar 2016 13:34:22 -0800 (PST) Subject: Re: [PATCH v2] sparc64: Add support for Application Data Integrity (ADI) References: <56DDC2B6.6020009@oracle.com> <56DDC3EB.8060909@oracle.com> <56DDC776.3040003@oracle.com> <20160307.141600.1873883635480850431.davem@davemloft.net> From: Khalid Aziz Message-ID: <56DDF3C4.7070701@oracle.com> Date: Mon, 7 Mar 2016 14:33:56 -0700 MIME-Version: 1.0 In-Reply-To: <20160307.141600.1873883635480850431.davem@davemloft.net> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: David Miller Cc: rob.gardner@oracle.com, corbet@lwn.net, akpm@linux-foundation.org, dingel@linux.vnet.ibm.com, bob.picco@oracle.com, kirill.shutemov@linux.intel.com, aneesh.kumar@linux.vnet.ibm.com, aarcange@redhat.com, arnd@arndb.de, sparclinux@vger.kernel.org, mhocko@suse.cz, chris.hyser@oracle.com, richard@nod.at, vbabka@suse.cz, koct9i@gmail.com, oleg@redhat.com, gthelen@google.com, jack@suse.cz, xiexiuqi@huawei.com, Vineet.Gupta1@synopsys.com, luto@kernel.org, ebiederm@xmission.com, bsegall@google.com, geert@linux-m68k.org, dave@stgolabs.net, adobriyan@gmail.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org On 03/07/2016 12:16 PM, David Miller wrote: > From: Khalid Aziz > Date: Mon, 7 Mar 2016 11:24:54 -0700 > >> Tags can be cleared by user by setting tag to 0. Tags are >> automatically cleared by the hardware when the mapping for a virtual >> address is removed from TSB (which is why swappable pages are a >> problem), so kernel does not have to do it as part of clean up. > > You might be able to crib some bits for the Tag in the swp_entry_t, it's > 64-bit and you can therefore steal bits from the offset field. > > That way you'll have the ADI tag in the page tables, ready to re-install > at swapin time. > That is a possibility but limited in scope. An address range covered by a single TTE can have large number of tags. Version tags are set on cacheline. In extreme case, one could set a tag for each set of 64-bytes in a page. Also tags are set completely in userspace and no transition occurs to kernel space, so kernel has no idea of what tags have been set. I have not found a way to query the MMU on tags. I will think some more about it. Thanks, Khalid -- 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