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Thu, 30 Oct 2025 15:34:34 +0000 (GMT) Date: Thu, 30 Oct 2025 16:34:33 +0100 From: Gerald Schaefer To: Heiko Carstens Cc: Luiz Capitulino , Alexander Gordeev , Vasily Gorbik , Christian Borntraeger , Joao Martins , David Hildenbrand , osalvador@suse.de, aneesh.kumar@kernel.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org Subject: Re: [PATCH] s390: Disable ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP Message-ID: <20251030163433.1b178a40@thinkpad-T15> In-Reply-To: <20251030145505.2764038-1-hca@linux.ibm.com> References: <20251030145505.2764038-1-hca@linux.ibm.com> X-Mailer: Claws Mail 4.3.1 (GTK 3.24.43; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=C/XkCAP+ c=1 sm=1 tr=0 ts=6903858f cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=kj9zAlcOel0A:10 a=x6icFKpwvdMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VwQbUJbxAAAA:8 a=20KFwNOVAAAA:8 a=VnNF1IyMAAAA:8 a=UHg0BC72YOLF96oe5NYA:9 a=CjuIK1q_8ugA:10 a=cPQSjfK2_nFv0Q5t_7PE:22 X-Proofpoint-GUID: 9LPMGJUUuyEQ-wsfG6v5PycWDrR69Kv7 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMDI4MDE2NiBTYWx0ZWRfX2NRgdtn/21oZ IP/FdEaETScIsttY7JZrrTnwOXcTAjEYjy/gcKhtO/q89fyY5RqgMM2Zz84QWOlwerqLl9GYzNU 7mNFTo7u97cWMiBFc0JcL/8pe67t3p9klJ8Z3unnb3+FXYb4avIdxXzpdiU41XTLcxkOnKAw57p mmOSPx+DH7qmY8W0MKakEld5nr4iQOA74Sjl8U232cb1nT5AxzxHaiMmR+B85s0JWNJ2xquY326 bdN81w+lgJmglZVAK91W8N2nW9LXCbVTRQBWr6bEmhf9qlQVSpx3bkmbTxUDMrRORzoHH+NOnF+ vKnNL4okgojDQCxfPEUfg0sQJVUMgNVSS76k5S2gZTH5SWGF6Wu/MyRKOSBl3Mh83Fp31ORoVgT 3s5tIZv597025Fuhr61/XNN6FjH/xA== X-Proofpoint-ORIG-GUID: 9LPMGJUUuyEQ-wsfG6v5PycWDrR69Kv7 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-10-30_05,2025-10-29_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 lowpriorityscore=0 impostorscore=0 adultscore=0 suspectscore=0 spamscore=0 phishscore=0 malwarescore=0 priorityscore=1501 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2510280166 On Thu, 30 Oct 2025 15:55:05 +0100 Heiko Carstens wrote: > As reported by Luiz Capitulino enabling HVO on s390 leads to reproducible > crashes. The problem is that kernel page tables are modified without > flushing corresponding TLB entries. > > Even if it looks like the empty flush_tlb_all() implementation on s390 is > the problem, it is actually a different problem: on s390 it is not allowed > to replace an active/valid page table entry with another valid page table > entry without the detour over an invalid entry. A direct replacement may > lead to random crashes and/or data corruption. > > In order to invalidate an entry special instructions have to be used > (e.g. ipte or idte). Alternatively there are also special instructions > available which allow to replace a valid entry with a different valid > entry (e.g. crdte or cspg). > > Given that the HVO code currently does not provide the hooks to allow for > an implementation which is compliant with the s390 architecture > requirements, disable ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP again, which is > basically a revert of the original patch which enabled it. > > Reported-by: Luiz Capitulino > Closes: https://lore.kernel.org/all/20251028153930.37107-1-luizcap@redhat.com/ > Fixes: 00a34d5a99c0 ("s390: select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP") > Cc: stable@vger.kernel.org > Signed-off-by: Heiko Carstens > --- > arch/s390/Kconfig | 1 - > 1 file changed, 1 deletion(-) Thanks! Reviewed-by: Gerald Schaefer