From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x226S76A33jf2RudYWOb9cUThScyuX2k6XXMdpP1+X7omk8OUNSqDTdwesu77ARwHbJse37Aa ARC-Seal: i=1; a=rsa-sha256; t=1519271521; cv=none; d=google.com; s=arc-20160816; b=RZCRcGzXH1v5dHBphgULV/62wQ3dULUevK8LX1pUo6RAfpWGux+hmJ3/5z/CP/IQAJ ATPEs4vlo4sYgzeELBzB4YNApTB7s7L417k8a/4MyIUknUkz6gikIZW9EIMmtFS8+TPW PVouDSFgCLVodUkwgO0sk1hXuU1jOg7IBPkwta0dgr4Z3U57ZxyjBTersCBmPdh/1eiS LOIcDniQddxm2Y59NCNhwU8xTteCOX9eF0CqpRBDgxWpga9+I9ml21hLUhhBpQgjEdTm pLHwLAv4bZ6xnyafbx0axtmL+op/lHsouz6DNNMvwabn6rvJvUU6yizprJSAT9dT0kLH GU+w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=message-id:content-transfer-encoding:mime-version:organization :references:in-reply-to:date:cc:to:from:subject :arc-authentication-results; bh=zwO/HHOr3JLDIG42x0LtQ0kDX/hGJHpqpq/1iK1tc4w=; b=gz0vo2VXwILcbOvJS29E+34Tg7YyIzfc9YGONeJCuypRG9JFSumOXh0Yo51Jh4umPV uqXu6cPBpBP2VCIxGzkKhn+GiKbCNaTJUcqD5z0ZxLYbSlvKb5IqbhzVMpn37zM+ktAJ 28nOKL5X7Jk8/wn9duVrDjTFRfJKeKJ2T1FiWJ1b5KWws7xHMZVoQ9Ldnyey0vCykB+E /dLU5T+8EY3MrKRRrACjsfWpmufuft+eWtLAckdlC6BUoRX+2JXQy7TTt9G50FgKhxoD 72slq4QM44x5kR7S2o4U/qYdNEZ4QGeaqJDlLYJ5WiJjfn7Q8mpc663g8mfGtvxu/nLN Ks0w== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of alastair@au1.ibm.com designates 148.163.156.1 as permitted sender) smtp.mailfrom=alastair@au1.ibm.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=ibm.com Authentication-Results: mx.google.com; spf=pass (google.com: domain of alastair@au1.ibm.com designates 148.163.156.1 as permitted sender) smtp.mailfrom=alastair@au1.ibm.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=ibm.com Subject: Re: [PATCH] ocxl: Add get_metadata IOCTL to share OCXL information to userspace From: "Alastair D'Silva" To: Balbir Singh , Frederic Barrat Cc: Arnd Bergmann , frederic.barrat@fr.ibm.com, Greg KH , "linux-kernel@vger.kernel.org" , linuxppc-dev , Andrew Donnellan Date: Thu, 22 Feb 2018 14:51:52 +1100 In-Reply-To: References: <20180221045736.7614-1-alastair@au1.ibm.com> Organization: IBM Australia Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.5 (3.26.5-1.fc27) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 18022203-0008-0000-0000-000004D2FCE6 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18022203-0009-0000-0000-00001E66073C Message-Id: <1519271512.2867.14.camel@au1.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-02-22_01:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1802220049 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1592985250939595866?= X-GMAIL-MSGID: =?utf-8?q?1593071655174191617?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Thu, 2018-02-22 at 14:46 +1100, Balbir Singh wrote: > lpc_size could be added. It's currently useless to the library, but > > doesn't > > hurt. The one which was giving me troubles on a previous version of > > this > > patch was the lpc numa node ID, since that was experimental code > > and felt > > out of place considering what's been upstreamed in skiboot and > > linux so far. > > > > Yeah, I think metadata will evolve for a while till it settle's down. > Since ocxl_ioctl_get_metadata is exposed via uapi, a newer program > calling an older kernel will never work, since the size of that > struct > will always be larger than what the OS supports and our > copy_to_user() > will fail. The other option is for the user program to try all > possible versions till one succeeds, that is bad as well. I think > there are a few ways around it, if we care about this combination. > > Balbir Singh. > We have a number of reserved members at the end of the struct which can be re-purposed for future information (with a corresponding bump of the version number). -- Alastair D'Silva Open Source Developer Linux Technology Centre, IBM Australia mob: 0423 762 819