From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Zenghui Yu <zenghui.yu@linux.dev>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: jgg@ziepe.ca, leon@kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
ljs@kernel.org, liam@infradead.org, vbabka@kernel.org,
rppt@kernel.org, surenb@google.com, mhocko@suse.com,
Alistair Popple <apopple@nvidia.com>
Subject: Re: "alloc_tag was not set" when running mm/ksft_hmm.sh
Date: Fri, 8 May 2026 13:53:43 +0200 [thread overview]
Message-ID: <10e4565a-b416-45d9-a8b0-cd32532b2630@kernel.org> (raw)
In-Reply-To: <be9a8bae-9223-4966-bba9-2cbe39c8f4de@linux.dev>
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?
--
Cheers,
David
next prev parent reply other threads:[~2026-05-08 11:53 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-06 15:42 "alloc_tag was not set" when running mm/ksft_hmm.sh Zenghui Yu
2026-05-08 11:53 ` David Hildenbrand (Arm) [this message]
2026-05-08 16:35 ` Alistair Popple
2026-05-11 12:19 ` Zenghui Yu
2026-05-11 12:47 ` David Hildenbrand (Arm)
2026-05-11 16:38 ` Zenghui Yu
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