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Mon, 12 Oct 2026 14:34:46 +0000 (GMT) Received: from li-008a6a4c-3549-11b2-a85c-c5cc2836eea2.ibm.com (unknown [9.224.92.206]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTPS; Mon, 12 Oct 2026 14:34:46 +0000 (GMT) Date: Mon, 12 Oct 2026 16:34:44 +0200 From: Alexander Gordeev To: Heiko Carstens Cc: Sven Schnelle , Vasily Gorbik , Christian Borntraeger , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org Subject: Re: [PATCH 2/4] s390/percpu: Drop unused output register from arch_this_cpu_add() Message-ID: <23b62609-3744-4b6b-8a80-3ae1b0edd07c-agordeev@linux.ibm.com> References: <20261012114249.2898572-1-hca@linux.ibm.com> <20261012114249.2898572-3-hca@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261012114249.2898572-3-hca@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: fjBf4eL24L17dT6IgpmlZFkG6lFSCzY0 X-Proofpoint-ORIG-GUID: fjBf4eL24L17dT6IgpmlZFkG6lFSCzY0 X-Authority-Analysis: v=2.4 cv=aqInmiZV c=1 sm=1 tr=0 ts=6accf00a cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=kj9zAlcOel0A:10 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VnNF1IyMAAAA:8 a=hrbHa4fqjneYn2M9ZQ8A:9 a=CjuIK1q_8ugA:10 X-Proofpoint-Spam-Info: AW1haW4tMjYxMDEyMDA1NiBTYWx0ZWRfX+V3gHRmi5Av6 xrna4MbCWGaoSeMygqinY3WZT74JyTWgQ8f9DeGt6zNnu3X4/elm+2xQ2cMP3j26GfZZMotyzfI WSix3uRYbcXpLpqAl+mQIxgewiwRCSM= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDEyMDA1NiBTYWx0ZWRfX65JycP2upIzI TdDCa6klsApuj/7tqEBjTTYNXAbucO0VKY1HpVm8pRVidXOxRh2Lp5A9jn+MTcy2+nA1X6ybyAe wVm3OsPXt/nvRcKgckcmrtTmSs72oHbCGPUvOZ8kimVm8ukGKGdt8P6sqCzO5t48oleqfKmWh2k IKz+3yGE8nw5Wn7cSd07+jzVsukv1HRl5ym8PJk8PuibGNnL0r5FP0v/eb5oGLUhVAFZOMgZBoq qPbEhzPgcc/8Ye5w685Ii/9PYdrZzpQihvqE77AffOnf9+thko65K2VwlZ/m0WtMvaocQnYrs/u rJWrqX74me2/XAlXM9u/DvZWvUdt2pBWE799LJJSbykEsGaNxnKnr7lNbSfh8pOs9zpfagvgl9E HziMIJIUSbRlKARS9jXgfZDsFvWc8qmOFqE+TxAcphI/nx9hTTbPLqpCUqtLC9uoxrcjoOuA2nm MfOr3E5VA3raTMdBPeQ== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-10-12_04,2026-10-09_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 clxscore=1015 spamscore=0 malwarescore=0 suspectscore=0 bulkscore=0 adultscore=0 impostorscore=0 priorityscore=1501 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610080000 definitions=main-2610120056 On Mon, Oct 12, 2026 at 01:42:47PM +0200, Heiko Carstens wrote: > The laa/laag instructions return the old memory content, but > arch_this_cpu_add() does not need it. Instead of allocating a dedicated > output register old__ just to discard the returned value, change the > val__ constraint from "d" to "+&d" so it is used as input/output > register. > > This reduces register pressure. > > Signed-off-by: Heiko Carstens > --- > arch/s390/include/asm/percpu.h | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) Acked-by: Alexander Gordeev