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bits=128/128); Wed, 13 May 2026 09:01:21 -0700 (PDT) Message-ID: Date: Wed, 13 May 2026 19:01:16 +0300 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-Proofpoint-GUID: 0BsklaQETYhmCBp1_5TLYlpJkKIaAvHB X-Authority-Analysis: v=2.4 cv=DOS/JSNb c=1 sm=1 tr=0 ts=6a04a054 cx=c_pps a=bS7HVuBVfinNPG3f6cIo3Q==: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=eoimf2acIAo5FJnRuUoq:22 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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