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<10e4565a-b416-45d9-a8b0-cd32532b2630@kernel.org> From: Zenghui Yu Message-ID: <2b46241c-158b-c9dd-9b81-a98366b2c9fb@huawei.com> Date: Mon, 11 May 2026 20:19:46 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: <10e4565a-b416-45d9-a8b0-cd32532b2630@kernel.org> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.219] X-ClientProxiedBy: kwepems100001.china.huawei.com (7.221.188.238) To kwepemk200017.china.huawei.com (7.202.194.83) X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 9EF0040008 X-Rspam-User: X-Stat-Signature: jwh19wefxwhkte9tk3qmhdnch38wcsq8 X-HE-Tag: 1778501999-355209 X-HE-Meta: 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 5YBFx6lf OCUskZLuNsp0tEVpDqGH4FaPhC6XozNyGKyRGeuxIlHXW7aDL3wj0o6AF55fy/vXpne/8Qc4Kt4hxMS2jszWqHNBSgyeesE8jPIhWovasPXy43cyV2zkplfcqVVbQg9ayDmigXgKyUwQL9x1YP7HmV/jtq0LgjkXjJF8hsXOMasjFiuJujfTFvdMQzXN/nx0FgJyk+fQADKHiaoWg9PDSoXqIfjLoAGHF9ZxK+FO+TvE15AaJqe/bRaus1ez4fmdXqxK68XZ7jYnL5zYNIxQtE8UJCplHqhPVPa9qrEFyLDIVWgosK3hNmmWtY+Q73ic+yItazsyZ9Dd+Z/ClSHYDOnwNUtVZA5GOdxO8EjCSNnc9f8BEdER7wHRZ/tc4AMKnSEdx Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026/5/8 19:53, 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 FYI this can be reproduced by running the migrate_partial_unmap_fault test case. TEST_F(hmm, migrate_partial_unmap_fault) { buffer->mirror = malloc(TWOMEG); buffer->ptr = map; // points to a THP /* Initialize buffer in system memory. */ for (i = 0, ptr = buffer->ptr; i < TWOMEG / sizeof(*ptr); ++i) ptr[i] = i; ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages); munmap(buffer->ptr, ONEMEG); /* Fault pages back to system memory and check them. */ for (i = 0, ptr = buffer->ptr; i < TWOMEG / sizeof(*ptr); ++i) if (i * sizeof(int) < 0 || i * sizeof(int) >= ONEMEG) ASSERT_EQ(ptr[i], i); // triggers a fault -> dmirror_devmem_fault() migrate_vma_setup() migrate_vma_collect_pmd() // !pte_present(pte) && folio_test_large(folio) migrate_vma_split_folio() split_folio() [...] __folio_split() { unmap_folio(); __folio_freeze_and_split_unmapped() { __split_unmapped_folio(); for (...) { zone_device_private_split_cb(.., new_folio); // -> dmirror_devmem_folio_split() which doesn't // set alloc tag for the backing system memory // page being split, i.e., rpage_tail } zone_device_private_split_cb(.., NULL); } remap_page(); for (...) free_folio_and_swap_cache(new_folio); // -> dmirror_devmem_free()/__free_page() which warns if // the page being freed doesn't have alloc tag set, in // alloc_tag_sub_check(). } The WARN disappears with the following diff. But I'm not sure if I've missed more important points (which is likely to happen ;-) ). diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c index ed1bdcf1f8ab..eefa2a739917 100644 --- a/lib/alloc_tag.c +++ b/lib/alloc_tag.c @@ -191,6 +191,7 @@ void pgalloc_tag_split(struct folio *folio, int old_order, int new_order) } } } +EXPORT_SYMBOL(pgalloc_tag_split); void pgalloc_tag_swap(struct folio *new, struct folio *old) { diff --git a/lib/test_hmm.c b/lib/test_hmm.c index 213504915737..3bec51828916 100644 --- a/lib/test_hmm.c +++ b/lib/test_hmm.c @@ -1713,6 +1713,7 @@ static void dmirror_devmem_folio_split(struct folio *head, struct folio *tail) rfolio = page_folio(rpage); if (tail == NULL) { + pgalloc_tag_split(rfolio, folio_order(rfolio), 0); folio_reset_order(rfolio); rfolio->mapping = NULL; folio_set_count(rfolio, 1); Thanks, Zenghui