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Wed, 13 May 2026 09:01:23 -0700 (PDT) X-Received: by 2002:a05:701b:2513:b0:134:a701:de8 with SMTP id a92af1059eb24-134a7010fd6mr983081c88.5.1778688081428; Wed, 13 May 2026 09:01:21 -0700 (PDT) Received: from [192.168.0.31] ([212.5.153.243]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-134b4e153dbsm2062086c88.12.2026.05.13.09.01.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 13 May 2026 09:01:21 -0700 (PDT) Message-ID: Date: Wed, 13 May 2026 19:01:16 +0300 Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drivers/base/memory: set mem->altmap after successful device registration To: "David Hildenbrand (Arm)" , akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-cxl@vger.kernel.org, osalvador@suse.de, gregkh@linuxfoundation.org, rafael@kernel.org, djakov@kernel.org References: <20260513130900.2204499-1-georgi.djakov@oss.qualcomm.com> Content-Language: en-US From: Georgi Djakov In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Authority-Analysis: v=2.4 cv=X4di7mTe c=1 sm=1 tr=0 ts=6a04a055 cx=c_pps a=JYo30EpNSr/tUYqK9jHPoA==:117 a=douLNevBrtimd63D7eljNA==:17 a=IkcTkHD0fZMA:10 a=NGcC8JguVDcA:10 a=s4-Qcg_JpJYA:10 a=sWKEhP36mHoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=yOCtJkima9RkubShWh1s:22 a=h-BE1Ed2neb_JwLtZIQA:9 a=QEXdDO2ut3YA:10 a=Fk4IpSoW4aLDllm1B1p-:22 X-Proofpoint-GUID: hLd21eWyYfqBZu5wXTKORzMa5ArMDP2u X-Proofpoint-ORIG-GUID: hLd21eWyYfqBZu5wXTKORzMa5ArMDP2u X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTEzMDE2MyBTYWx0ZWRfXw0VrpmvMZdH7 4ECNDn9bomGnZhJkU2NKtduD56UrcRdC2U7A1aO5Hc0M9yG4wW4dk9tF3zwEBUVKkArUpwJMFXm Lp0DCR3otrAQJFUWyFUwFONtcmYfARADOKa1BwrkHzvRkonHgexBrhSOEp7oToT7ia98mvqWc5R 4cVLNRfDFgrVjQOgZ5SJYus7gYI/Ns47Nhl7QHhoqPHj+Fk02oaVIQo3IuSe7eqhUDzYl3NbL7p 79kwYh2rhchfhGTRLdURWl7qsdhTCjKOqtBoAHj2IpPb13VRt1ffVvF0frSfjBbbUWiel/CGd0Y S6voZNrs2OhIAvH+xOrFxQ/qbhSMEZheLUEjUPmoIqtTzMhFT92oIeVFdX3Pm32TUukSmyhqAmy k8cOhg8VdsUzKumvnxoR53EECS3QTUF3Z95Xr0SvWL96MQWUPHpe61PaZ9gRAhjhq3Q5gQ+SRaI Ux9ePxYaPrBVZwgnthA== 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=2026-05-13_01,2026-05-13_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 priorityscore=1501 lowpriorityscore=0 adultscore=0 phishscore=0 malwarescore=0 suspectscore=0 spamscore=0 clxscore=1015 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605050000 definitions=main-2605130163 Hi David, On 5/13/2026 4:20 PM, David Hildenbrand (Arm) wrote: > On 5/13/26 15:14, David Hildenbrand (Arm) wrote: >> On 5/13/26 15:09, Georgi Djakov wrote: >>> If __add_memory_block() fails at xa_store() (under memory pressure >>> for example), device_unregister() is called, which eventually >>> triggers memory_block_release() with mem->altmap still set, causing >>> a WARN_ON(mem->altmap). >>> >>> WARNING: CPU: 1 PID: 76 at drivers/base/memory.c:96 memory_block_release+0x28/0x30 >>> Call trace: >>> memory_block_release+0x28/0x30 (P) >>> kobject_put+0xc8/0x1bc >>> device_unregister+0x2c/0x68 >>> add_memory_block+0x1b4/0x214 >>> create_memory_block_devices+0x9c/0xfc >>> create_altmaps_and_memory_blocks+0x130/0x1cc >>> add_memory_resource+0x10c/0x21c >>> add_memory_driver_managed+0xb8/0xe8 >>> virtio_mem_add_memory+0xa4/0x194 [virtio_mem] >>> virtio_mem_sbm_plug_and_add_mb+0xc8/0x16c [virtio_mem] >>> virtio_mem_run_wq+0xea8/0x1088 [virtio_mem] >>> process_scheduled_works+0x18c/0x300 >>> worker_thread+0x1dc/0x2b8 >>> kthread+0x1ac/0x1f4 >>> ret_from_fork+0x10/0x20 >>> >>> Fix this by delaying the assignment of mem->altmap until after >>> __add_memory_block() has succeeded. >> >> Something does not add up here. How do you get an altmap with virtio-mem? > > That patch itself makes sense, but the callchain does not make sense. > > virtio_mem does not set MHP_MEMMAP_ON_MEMORY, so it should never reach > create_altmaps_and_memory_blocks()? I have some out of tree virtio_mem patches on top that helped to trigger this. Sorry for not mentioning it. Should i remove the callchain from the commit text to avoid confusion? Thanks, Georgi