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Fri, 25 Apr 2025 14:09:30 +0000 (GMT) Date: Fri, 25 Apr 2025 16:09:29 +0200 From: Heiko Carstens To: Niklas Schnelle Cc: Thomas Huth , Farhan Ali , qemu-devel@nongnu.org, alex.williamson@redhat.com, stefanha@redhat.com, mjrosato@linux.ibm.com, philmd@linaro.org, kwolf@redhat.com, hreitz@redhat.com, fam@euphon.net Subject: Re: [PATCH v5 1/3] util: Add functions for s390x mmio read/write Message-ID: <20250425140929.7180Fdb-hca@linux.ibm.com> References: <20250417173801.827-1-alifm@linux.ibm.com> <20250417173801.827-2-alifm@linux.ibm.com> <06f9244c-671c-4215-9d20-7bb69194fae6@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=aZRhnQot c=1 sm=1 tr=0 ts=680b979f cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=kj9zAlcOel0A:10 a=XR8D0OoHHMoA:10 a=RASPwGoQohVzQn-ICVUA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-GUID: CsPJY9RCwawA00jXUpyDOsV-03Pz85LR X-Proofpoint-ORIG-GUID: CsPJY9RCwawA00jXUpyDOsV-03Pz85LR X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNDI1MDEwMCBTYWx0ZWRfXxLpRJi4bw5ZJ ttChqsdtfMQhavw22VYevgmVI/eMAZD9L6FCC9IkA8f5Ho3lx7RtZx1M/l6tXNM9isO3K2eVYVr gk6M3wvJLm4rc9apjmeYnZvQ+Mj3dnmPjQxjdi9BL8Aikqn0lg06R4ou+CHY9B93Mdd4SQzZ4u1 DQPzVK3XEjQwdr+eYiOld9Ws8ORLqQgiktDMUbgAoG/hmfQmAAkx4rq7uUKuJQNDudFOBkr7kFA BZfNSZYGxPpwdDQrbMGD22l+gdx9CNZVtHLO1LenarGtaYOprJw29Vg7xrgBg/F5QqHmUfMQg2h 3JcXOCIljoTSYwbkRmZmLh+2M5uk7oClvOgPsCs+ZutdtoonPzuQqKNlJEJnpcQdpbuvrZ8RQIT usy1bV5sw4csqgrmDXhpRCrRBk5avmaf6+Bgf0s/ADlsP5PazMTajGmDuqB7x369+6XJ7Wxk X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-04-25_04,2025-04-24_02,2025-02-21_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 bulkscore=0 lowpriorityscore=0 suspectscore=0 adultscore=0 priorityscore=1501 clxscore=1011 mlxlogscore=433 impostorscore=0 mlxscore=0 malwarescore=0 phishscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2504070000 definitions=main-2504250100 Received-SPF: pass client-ip=148.163.158.5; envelope-from=hca@linux.ibm.com; helo=mx0b-001b2d01.pphosted.com X-Spam_score_int: -26 X-Spam_score: -2.7 X-Spam_bar: -- X-Spam_report: (-2.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Fri, Apr 25, 2025 at 12:29:35PM +0200, Niklas Schnelle wrote: > On Fri, 2025-04-25 at 11:00 +0200, Thomas Huth wrote: > > On 17/04/2025 19.37, Farhan Ali wrote: > > > + asm volatile( > > > + /* pcilgi */ > > > + ".insn rre,0xb9d60000,%[val],%[ioaddr_len]\n" > > > + "ipm %[cc]\n" > > > + "srl %[cc],28\n" > > > + : [cc] "=d"(cc), [val] "=d"(val), > > > + [ioaddr_len] "+&d"(ioaddr_len.pair) :: "cc"); > > > > Do we need the "&" modifier here? ... at least the kernel does not seem to > > use it ... > > From my understanding it's not strictly needed, but I also used it in > the rdma-core user-space code where I had pointed Farhan. I looked at It is not needed, since all inputs are consumed before to any output is written to. > > > + asm volatile ( > > > + /* pcistgi */ > > > + ".insn rre,0xb9d40000,%[val],%[ioaddr_len]\n" > > > + : [ioaddr_len] "+&d" (ioaddr_len.pair) > > > > dito Same here, it is not needed.