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Tue, 22 Sep 2026 11:06:35 +0000 (GMT) Received: from [9.224.77.173] (unknown [9.224.77.173]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 22 Sep 2026 11:06:35 +0000 (GMT) Message-ID: <1ae860b1-6aaf-4930-a571-8d8cc7a5c461@linux.ibm.com> Date: Tue, 22 Sep 2026 13:06:35 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] s390/uv: Rework page allocation for guest variable storage area To: Heiko Carstens , Janosch Frank , Claudio Imbrenda , David Hildenbrand Cc: Vasily Gorbik , Sven Schnelle , Alexander Gordeev , kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260915144307.2367089-1-hca@linux.ibm.com> Content-Language: en-US From: Christian Borntraeger In-Reply-To: <20260915144307.2367089-1-hca@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=V/XoQuni c=1 sm=1 tr=0 ts=6ab26140 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=WZdyr50IRSPTGao3C8IA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: tz4D_sfIADCO0qhN6CVjqBDevddrNPdo X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTIyMDE2MCBTYWx0ZWRfXyU6roT7CCYgT uF0xeMi2acvWYIHX5Rz3RO7M3Zh7B0w8ZgmgOvhqxi3sS2hOLZJNcNy8IkhjdtC16XMM8GtvsNg 4hukspwWQPiChSoGF+xry6mGJMrS98iT5rRBJGvhGPEGM4q93UiXyaftsF5ColbDSscO6EsiS4l +Zugl+m4L7xCDEmZLgvidw5UhN4LwrCcXnFMhkvmmg4EML3ncA6Fx8jml2h/IUQLKuAJqpQ9AHj Rh+SuC1y+N+w7k0dDJc4hSpvFbfcaxsH0WG8mFKnuxtJPvspk0KEGG7kVGso8EIVeZdna6q90I6 gnzRZUu+J2UwOJckwAR9JPeADRPAQPMt474NzAwILypHokgBtX+QaS8G/ByX1EQDyq0ne6OSsXW pEqWlLAbfI7W6MHMuv3DrPXhC7wiZEcauxk5Yp26ZM+SEdpzaqVyrcyApexZsC82gNTbMcGKLl1 fqAsGBE20ozJ5meWlSQ== X-Proofpoint-Spam-Info: AW1haW4tMjYwOTIyMDE2MCBTYWx0ZWRfX6lSlNrePWOnH kLxPsNda5IKsJGBdsZsFUkEbcYsZiV9Dvs8aJr+sIW3Xl74/c/CkkubGxvC/L1dQyx4V2OlAO1a qLJy5+/wNWtoQzpLnQaGIfdCG4DHAkU= X-Proofpoint-GUID: tz4D_sfIADCO0qhN6CVjqBDevddrNPdo 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=2026-09-21_07,2026-09-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 spamscore=0 malwarescore=0 clxscore=1015 phishscore=0 bulkscore=0 adultscore=0 lowpriorityscore=0 impostorscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609220160 Am 15.09.26 um 16:43 schrieb Heiko Carstens: > Alexander Gordeev reported that the allocation of pages of the > guest variable storage area via the uv_alloc_range_cb() callback > of apply_to_page_range() will cause problems as soon as s390 fully > supports lazy mmu mode. > > Problem is that uv_alloc_range_cb() allocates pages with GFP_KERNEL while > preemption would be disabled. This would result in reports like this: > > BUG: sleeping function called from invalid context at ./include/linux/sched/mm.h:322 > in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 6092, name: qemu-kvm > preempt_count: 1, expected: 0 > ... > Call Trace: > dump_stack_lvl+0xae/0x108 > __might_resched+0x1de/0x2f0 > prepare_alloc_pages+0x1ba/0x220 > __alloc_frozen_pages_noprof+0xc6/0x390 > alloc_pages_mpol+0xe6/0x220 > alloc_frozen_pages_noprof+0x5c/0x80 > alloc_pages_noprof+0x22/0x80 > uv_alloc_range_cb+0x30/0x300 > apply_to_pte_range+0x11a/0x3b0 > apply_to_pmd_range+0x13a/0x250 > __apply_to_page_range+0x232/0x4d0 > apply_to_page_range+0x28/0x40 > uv_alloc_stor_var+0x5e/0x90 > kvm_s390_pv_alloc_vm+0x118/0x1e0 [kvm] > kvm_s390_pv_init_vm+0x84/0x2e0 [kvm] > kvm_s390_handle_pv+0x502/0xf70 [kvm] > kvm_arch_vm_ioctl+0x234/0xdd0 [kvm] > kvm_vm_ioctl+0x33a/0x890 [kvm] > __s390x_sys_ioctl+0xfa/0x130 > __do_syscall+0x1fc/0x700 > system_call+0x72/0x90 > > Preallocate the pages and make use of vm_area_map_pages() to address this > potential future bug. > > Reported-by: Alexander Gordeev > Closes: https://lore.kernel.org/all/e9449c63-b8d2-4ed9-a184-7dcab3e8dfce-agordeev@linux.ibm.com > Signed-off-by: Heiko Carstens Thanks applied. Will queue for the kvms390 tree after some CI runs.