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Fri, 2 Oct 2026 12:30:09 +0000 (GMT) Received: from li-008a6a4c-3549-11b2-a85c-c5cc2836eea2.ibm.com (unknown [9.224.92.206]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTPS; Fri, 2 Oct 2026 12:30:09 +0000 (GMT) Date: Fri, 2 Oct 2026 14:30:08 +0200 From: Alexander Gordeev To: Heiko Carstens Cc: Gerald Schaefer , Christian Borntraeger , Vasily Gorbik , Claudio Imbrenda , Andrey Ryabinin , linux-s390@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com Subject: Re: [PATCH v7 2/4] s390/mm: Batch PTE updates in lazy MMU mode Message-ID: <4ee1e4e6-4ecb-4fec-a481-c4f2236eb514-agordeev@linux.ibm.com> References: <20260824104048.11040Cdc-hca@linux.ibm.com> <20261001082143.23106A21-hca@linux.ibm.com> <15c64970-d54e-4b8f-96f6-50c021079a94-agordeev@linux.ibm.com> <20261001154117.23106Da3-hca@linux.ibm.com> <20261002084315.21787Ba6-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: <20261002084315.21787Ba6-hca@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=FYWiV5+6 c=1 sm=1 tr=0 ts=6abfa3d6 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=kj9zAlcOel0A:10 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=bLWW0i0dwBbJnIBF-2cA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-Spam-Info: AW1haW4tMjYxMDAyMDA0OCBTYWx0ZWRfX7RnYetFSSEIx wpqVm/IrnUEY5C2fgABcIk9Te7ob3SotikBDvg1coinJOCfv9Qfvpd8lURzGrP8WrGcYNa+j7qf FVGPvEwbxl2r/Q9iA6mmrjzoIhmRKmk= X-Proofpoint-ORIG-GUID: xHiclTGYKBP7O7nDjmVOh4hlN__ELI1l X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDAyMDA0OCBTYWx0ZWRfXwytMGQg8vIEM 4yip4Bs04yYfo9INyCYwKPcTh3piGH9HIpegL9lSdM4BaKOb62tPPWSh+vdNbHdB7AL+JeQXOTL ZNd+XAeW7L0zc0c5EnwMYwv9OA/SOEteRm0QXv+GxoeaN8RQ5XqOD9C0NxP4iRS7BJvFQ1fiqhq 6/+aguB8WZHSp+gsUDn3nRFhYmb1uGWA/RTxiR1oyDs1T8J7MuUI8DzF+9paUEovig7Q69KELEQ bzAKzyPk9IVX0+c7Kcl6QapmwqP0tcOwLHepzmsN7gWk3kSRN3WMc9iAwFyTLiFdwHa/V7yemOU 7K/bLhEdqtuAgdJ8nHaFp3+85DI3zT0spApuzkFLqBB1knFeYOzjGSMTbxjGteFk4O2Ff8nMFc4 VQ+AxVIKac+GwJvOOeeiaxIGCDO6RN/O9N3xi0y+MvHFP2jWIoghOj0fIyoV3QgH/8Ftmvpq8Jo 0OcIqn6F8xa9NiDobBA== X-Proofpoint-GUID: pWRTe5PpEKDMeNbbBBdXZ2uzDWYlbNeM 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=2026-10-02_03,2026-10-01_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 clxscore=1015 impostorscore=0 spamscore=0 phishscore=0 priorityscore=1501 malwarescore=0 bulkscore=0 lowpriorityscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2610020048 On Fri, Oct 02, 2026 at 10:43:15AM +0200, Heiko Carstens wrote: > > > Good point. But still, do you think it worth dropping the KASAN check? > > > > KASAN check for lowcore? I don't think we care - this is initialized to zero > > anyway, so what could go wrong? Also given how frequently these operations are > > used, yes, please drop KASAN checks. > > Of course you could still add an explicit KASAN/KCSAN check by adding an > instrument_read() call (see e.g. s390's fpu-insn.h, which has plenty of them). > > But why do you think that would be helpful for a lowcore field, where it is > known that is initialized to zero? What am I missing? Nothing. I am going to adopt all your suggestions into the new version. Thanks!