From: Alistair Popple <apopple@nvidia.com>
To: "David Hildenbrand (Arm)" <david@kernel.org>
Cc: Zenghui Yu <zenghui.yu@linux.dev>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org, 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
Subject: Re: "alloc_tag was not set" when running mm/ksft_hmm.sh
Date: Sat, 9 May 2026 02:35:56 +1000 [thread overview]
Message-ID: <af4HwfEtza4JYxEd@nvdebian.thelocal> (raw)
In-Reply-To: <10e4565a-b416-45d9-a8b0-cd32532b2630@kernel.org>
On 2026-05-08 at 21:53 +1000, "David Hildenbrand (Arm)" <david@kernel.org> 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
prev parent reply other threads:[~2026-05-08 16:36 UTC|newest]
Thread overview: 3+ 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)
2026-05-08 16:35 ` Alistair Popple [this message]
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