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From: Alistair Popple To: "David Hildenbrand (Arm)" Cc: Zenghui Yu , linux-mm@kvack.org, linux-kernel@vger.kernel.org, jgg@ziepe.ca, leon@kernel.org, Andrew Morton , ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com Subject: Re: "alloc_tag was not set" when running mm/ksft_hmm.sh Message-ID: References: <10e4565a-b416-45d9-a8b0-cd32532b2630@kernel.org> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <10e4565a-b416-45d9-a8b0-cd32532b2630@kernel.org> X-ClientProxiedBy: SY5P300CA0043.AUSP300.PROD.OUTLOOK.COM (2603:10c6:10:1fd::16) To DS0PR12MB7726.namprd12.prod.outlook.com (2603:10b6:8:130::6) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS0PR12MB7726:EE_|CY5PR12MB6597:EE_ X-MS-Office365-Filtering-Correlation-Id: 83319044-775f-4638-1d2e-08dead1fe771 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X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: xb8X/iKxvmnjRTVGvNizPrEFuZSgd/QjK4kLZxfQIPSOw0sABhOMdiKQgGhGlmpCni0wBEy0M3r0cA4QQvDYCg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY5PR12MB6597 On 2026-05-08 at 21:53 +1000, "David Hildenbrand (Arm)" wrote... > On 5/6/26 17:42, Zenghui Yu wrote: > > Hi all, > > > > Running mm/ksft_hmm.sh triggers the following splat: > > > > ------------[ cut here ]------------ > > alloc_tag was not set > > WARNING: ./include/linux/alloc_tag.h:164 at ___free_pages+0x2a0/0x2d0, > > CPU#5: hmm-tests/2020 > > Modules linked in: test_hmm rfkill drm backlight fuse > > CPU: 5 UID: 0 PID: 2020 Comm: hmm-tests Kdump: loaded Not tainted > > 7.1.0-rc2-00099-gadc1e5c6203c-dirty #285 PREEMPT > > Hardware name: QEMU QEMU Virtual Machine, BIOS > > edk2-stable202408-prebuilt.qemu.org 08/13/2024 > > pstate: 61400005 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) > > pc : ___free_pages+0x2a0/0x2d0 > > lr : ___free_pages+0x2a0/0x2d0 > > sp : ffff80008345b530 > > x29: ffff80008345b530 x28: ffff80008345b700 x27: ffffffffbfff8040 > > x26: ffff0000c41cb360 x25: ffff0000c0c64008 x24: ffff800081aae400 > > x23: 05ffff0000000200 x22: 0000000000000000 x21: 0000000000000000 > > x20: fffffdffc5f20040 x19: 0000000000000000 x18: fffffffffffe7c78 > > x17: 0000000000000000 x16: 0000000000000000 x15: fffffffffffe7c98 > > x14: 00000000000001d1 x13: ffff8000818f3d58 x12: 0000000000000573 > > x11: fffffffffffe7c98 x10: ffff80008194bd58 x9 : 3ffffffffffff000 > > x8 : ffff8000818f3d58 x7 : ffff80008194bd58 x6 : 0000000000000000 > > x5 : ffff0001fedb1088 x4 : 0000000000000001 x3 : 0000000000000000 > > x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0000c7f58000 > > Call trace: > > ___free_pages+0x2a0/0x2d0 (P) > > __free_pages+0x14/0x20 > > dmirror_devmem_free+0x13c/0x158 [test_hmm] > > free_zone_device_folio+0x144/0x1e4 > > __folio_put+0x124/0x130 > > free_folio_and_swap_cache+0xa8/0xcc > > __folio_split+0x664/0x7fc > > split_folio_to_list+0x50/0x5c > > migrate_vma_split_folio+0x13c/0x25c > > migrate_vma_collect_pmd+0xed4/0xf68 > > walk_pgd_range+0x598/0x9a0 > > __walk_page_range+0x90/0x1a0 > > walk_page_range_mm_unsafe+0x194/0x20c > > walk_page_range+0x20/0x2c > > migrate_vma_setup+0x18c/0x224 > > dmirror_devmem_fault+0x188/0x2b8 [test_hmm] > > do_swap_page+0x1458/0x185c > > __handle_mm_fault+0x85c/0x1ba0 > > handle_mm_fault+0xb0/0x290 > > do_page_fault+0x1f8/0x6f8 > > do_translation_fault+0x60/0x6c > > do_mem_abort+0x44/0x94 > > el0_da+0x30/0xdc > > el0t_64_sync_handler+0xd0/0xe4 > > el0t_64_sync+0x198/0x19c > > ---[ end trace 0000000000000000 ]--- > > lib/test_hmm.c:705 module test_hmm func:dmirror_devmem_alloc_page has > > 16744448 allocated at module unload > > > > > > It was tested on kernel built with arm64's virt.config and > > > > +CONFIG_ZONE_DEVICE=y > > +CONFIG_DEVICE_PRIVATE=y > > +CONFIG_TEST_HMM=m > > +CONFIG_MEM_ALLOC_PROFILING=y > > +CONFIG_MEM_ALLOC_PROFILING_DEBUG=y > > I assume there is a weird interaction between alloc tags and simulated > ZONE_DEVICE memory in test_hmm.c > > @Alistair, any idea? I haven't managed to reproduce this but could imagine that would be the problem - not sure page_ext is supported for ZONE_DEVICE PRIVATE pages. I'm still travelling back from LSFMM so will take a closer look next week. Thanks! - Alistair > -- > Cheers, > > David