From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from canpmsgout03.his.huawei.com (canpmsgout03.his.huawei.com [113.46.200.218]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7A03B36C0C3 for ; Mon, 11 May 2026 12:19:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.218 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778501999; cv=none; b=hf4dnZHf3GYJkXs1ukxmn2PgApBs/5ZdqCBL3FtnWjoGDTTg15doYOaZglZh+B+T1q4HGfQr137i5rXHNHRX8e8fm0tBbJB0S3jinbtAf5AaCeA3SY2dpFo15bypjS5DRBVmYKEwnYCjy6HcqH2ScnBjiryPKdUu9NQoNlHGMlU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778501999; c=relaxed/simple; bh=OpJUGGOYo/vyOd+wtHVHXg5cq0AkVI58TyOteIR/ZKI=; h=Subject:To:CC:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=Orp3P3CgLNFpb9ujrZRRusXCS+D4yisGzEuRztTG2XEfylByE3vKGLYTFS1sGuuZKHJcaQ+cHlLU4HFQrpYTNmXXbFN7Xd/BcOaPiRoVi6/dXjX2diAA2WfG5y3tXOZTy8c/3/7PXfnFakwMIiY6/goivwE/fDVhY+7N5syHkkc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b=Bh5dXj92; arc=none smtp.client-ip=113.46.200.218 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b="Bh5dXj92" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=dCZIFtJXMuE+2/COrqhhAueJybF64/skKJvrKCDcOGM=; b=Bh5dXj92XABk0Z6o9gsjDjMJJilr6EB2ssykDKq4GGLCxFvle5JubTYP/v3JgYYj5Cbt1sYem ZkFXZ6wkVSly7b8lmNLEjtSMewNBHToQBu93c8Oura37K4ZnfIUmQAP3/Wt/7BrvgXG9ZnTmhBr bf0mdP4xkLGG0Xmou/XMcOk= Received: from mail.maildlp.com (unknown [172.19.162.144]) by canpmsgout03.his.huawei.com (SkyGuard) with ESMTPS id 4gDdsK4gRHzpT0B; Mon, 11 May 2026 20:12:53 +0800 (CST) Received: from kwepemk200017.china.huawei.com (unknown [7.202.194.83]) by mail.maildlp.com (Postfix) with ESMTPS id C8C014056D; Mon, 11 May 2026 20:19:51 +0800 (CST) Received: from [10.174.178.219] (10.174.178.219) by kwepemk200017.china.huawei.com (7.202.194.83) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Mon, 11 May 2026 20:19:50 +0800 Subject: Re: "alloc_tag was not set" when running mm/ksft_hmm.sh To: "David Hildenbrand (Arm)" CC: Zenghui Yu , , , , , Andrew Morton , , , , , , , Alistair Popple References: <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 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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-ClientProxiedBy: kwepems100001.china.huawei.com (7.221.188.238) To kwepemk200017.china.huawei.com (7.202.194.83) 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