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Fri, 15 May 2026 16:28:06 +0000 (GMT) Received: from osiris (unknown [9.87.152.91]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTPS; Fri, 15 May 2026 16:28:06 +0000 (GMT) Date: Fri, 15 May 2026 18:28:04 +0200 From: Heiko Carstens To: Yang Shi Cc: "David Hildenbrand (Arm)" , cl@gentwo.org, dennis@kernel.org, tj@kernel.org, urezki@gmail.com, catalin.marinas@arm.com, will@kernel.org, ryan.roberts@arm.com, akpm@linux-foundation.org, gor@linux.ibm.com, agordeev@linux.ibm.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [RFC v1 PATCH 0/11] Optimize this_cpu_*() ops for non-x86 (ARM64 for this series) Message-ID: <20260515162804.10935A18-hca@linux.ibm.com> References: <20260429170758.3018959-1-yang@os.amperecomputing.com> <583d5984-fc21-4204-9845-8ceabacf823f@os.amperecomputing.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <583d5984-fc21-4204-9845-8ceabacf823f@os.amperecomputing.com> X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: wqAuYEqpyC0PwdB9XTu9vOodcN-WAZSN X-Authority-Analysis: v=2.4 cv=duXrzVg4 c=1 sm=1 tr=0 ts=6a07499c cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=kj9zAlcOel0A:10 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=Ilrfog-IFM-LmiIkkiEA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-GUID: Ep4EDxbuyWSfO4E6e2i8hUChjCMZkeqE X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTE1MDE2NCBTYWx0ZWRfX9QwzjTNjAdg8 zvaaTNbk7r8YnJhAfC4qzFf+enpfMiIs7SYxiwu3DMBBqBGH0HiNNZYunznOi4KY56xMf7NIqVG nXBsIwP+a0lHialoCZBVoZ6B0GzN54eafdP/8K0lgA/d1ckJHWKBnE7lcuGBibul+pQVHhhpXOJ AQ6BLt9FgcMdBzPP7o/CGcVexl+YW1Kc9uRXyf67j0gdJKE/cd1DOK8H0qKqW1i+TzRU1SY2KBZ B4IUn5DCyIHE9R1SaS8rWspYke+SDb+8fvmpuJGJTd7Kvd9KHgtKMJ8zLZ4ndyrJBLvCPIg7XfN 4C/s0dcQnw2okOJU+kymeT7U5RM8sabO0TXiTHPzzOqPU3KDr34RfIv/QgNkZAKsNUWYAOlKjV3 7IhpOz8OzrE2bthGyY7RvHK5gEDeM7/srz53S5v86y5jKY7PhuIKPn2dAk51DUtHGQOX5mBiVSf 1AF+e1H5nADyY2v6RxQ== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-05-15_04,2026-05-15_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 clxscore=1015 priorityscore=1501 phishscore=0 bulkscore=0 adultscore=0 impostorscore=0 lowpriorityscore=0 suspectscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605130000 definitions=main-2605150164 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260515_092824_758805_7BE0DEEC X-CRM114-Status: GOOD ( 15.67 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, May 13, 2026 at 05:00:19PM -0700, Yang Shi wrote: > On 5/12/26 2:02 AM, David Hildenbrand (Arm) wrote: > > There was quite some feedback during the LSF/MM session, what's the current plan? ... > I'm not sure whether S390 folks will implement this on S390 or not, anyway > they are cc'ed. I'm not sure yet, however after I had a look at the architecture documentation a couple of weeks ago, I think it shouldn't be too hard to get this working on s390 as well. I was a bit concerned about TLB flushing, if changes to the kernel mapping happen with per-cpu page tables, but as of now I believe this shouldn't cause any harm (famous last words...).