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Message-ID: <202602031458.obPf0uoY-lkp@intel.com>
Date: Tue, 3 Feb 2026 14:32:39 +0800
From: kernel test robot <lkp@...el.com>
To: mpenttil@...hat.com, linux-mm@...ck.org
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
Mika Penttilä <mpenttil@...hat.com>,
David Hildenbrand <david@...hat.com>,
Jason Gunthorpe <jgg@...dia.com>,
Leon Romanovsky <leonro@...dia.com>,
Alistair Popple <apopple@...dia.com>,
Balbir Singh <balbirs@...dia.com>, Zi Yan <ziy@...dia.com>,
Matthew Brost <matthew.brost@...el.com>
Subject: Re: [PATCH v4 1/3] mm: unified hmm fault and migrate device pagewalk
paths
Hi,
kernel test robot noticed the following build errors:
[auto build test ERROR on 18f7fcd5e69a04df57b563360b88be72471d6b62]
url: https://github.com/intel-lab-lkp/linux/commits/mpenttil-redhat-com/mm-unified-hmm-fault-and-migrate-device-pagewalk-paths/20260202-192748
base: 18f7fcd5e69a04df57b563360b88be72471d6b62
patch link: https://lore.kernel.org/r/20260202112622.2104213-2-mpenttil%40redhat.com
patch subject: [PATCH v4 1/3] mm: unified hmm fault and migrate device pagewalk paths
config: x86_64-randconfig-101-20260202 (https://download.01.org/0day-ci/archive/20260203/202602031458.obPf0uoY-lkp@intel.com/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260203/202602031458.obPf0uoY-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602031458.obPf0uoY-lkp@intel.com/
All errors (new ones prefixed by >>):
ld: mm/hmm.o: in function `hmm_vma_walk_pmd':
>> mm/hmm.c:1028:(.text+0x21ab): undefined reference to `hmm_vma_handle_pmd'
vim +1028 mm/hmm.c
936
937 static int hmm_vma_walk_pmd(pmd_t *pmdp,
938 unsigned long start,
939 unsigned long end,
940 struct mm_walk *walk)
941 {
942 struct hmm_vma_walk *hmm_vma_walk = walk->private;
943 struct hmm_range *range = hmm_vma_walk->range;
944 unsigned long *hmm_pfns =
945 &range->hmm_pfns[(start - range->start) >> PAGE_SHIFT];
946 unsigned long npages = (end - start) >> PAGE_SHIFT;
947 struct mm_struct *mm = walk->vma->vm_mm;
948 unsigned long addr = start;
949 enum migrate_vma_info minfo;
950 unsigned long i;
951 pte_t *ptep;
952 pmd_t pmd;
953 int r = 0;
954
955 minfo = hmm_select_migrate(range);
956
957 again:
958 hmm_vma_walk->ptelocked = false;
959 hmm_vma_walk->pmdlocked = false;
960
961 if (minfo) {
962 hmm_vma_walk->ptl = pmd_lock(mm, pmdp);
963 hmm_vma_walk->pmdlocked = true;
964 pmd = pmdp_get(pmdp);
965 } else
966 pmd = pmdp_get_lockless(pmdp);
967
968 if (pmd_none(pmd)) {
969 r = hmm_vma_walk_hole(start, end, -1, walk);
970
971 if (hmm_vma_walk->pmdlocked) {
972 spin_unlock(hmm_vma_walk->ptl);
973 hmm_vma_walk->pmdlocked = false;
974 }
975 return r;
976 }
977
978 if (thp_migration_supported() && pmd_is_migration_entry(pmd)) {
979 if (!minfo) {
980 if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0)) {
981 hmm_vma_walk->last = addr;
982 pmd_migration_entry_wait(walk->mm, pmdp);
983 return -EBUSY;
984 }
985 }
986 for (i = 0; addr < end; addr += PAGE_SIZE, i++)
987 hmm_pfns[i] &= HMM_PFN_INOUT_FLAGS;
988
989 if (hmm_vma_walk->pmdlocked) {
990 spin_unlock(hmm_vma_walk->ptl);
991 hmm_vma_walk->pmdlocked = false;
992 }
993
994 return 0;
995 }
996
997 if (pmd_trans_huge(pmd) || !pmd_present(pmd)) {
998
999 if (!pmd_present(pmd)) {
1000 r = hmm_vma_handle_absent_pmd(walk, start, end, hmm_pfns,
1001 pmd);
1002 // If not migrating we are done
1003 if (r || !minfo) {
1004 if (hmm_vma_walk->pmdlocked) {
1005 spin_unlock(hmm_vma_walk->ptl);
1006 hmm_vma_walk->pmdlocked = false;
1007 }
1008 return r;
1009 }
1010 } else {
1011
1012 /*
1013 * No need to take pmd_lock here if not migrating,
1014 * even if some other thread is splitting the huge
1015 * pmd we will get that event through mmu_notifier callback.
1016 *
1017 * So just read pmd value and check again it's a transparent
1018 * huge or device mapping one and compute corresponding pfn
1019 * values.
1020 */
1021
1022 if (!minfo) {
1023 pmd = pmdp_get_lockless(pmdp);
1024 if (!pmd_trans_huge(pmd))
1025 goto again;
1026 }
1027
> 1028 r = hmm_vma_handle_pmd(walk, addr, end, hmm_pfns, pmd);
1029
1030 // If not migrating we are done
1031 if (r || !minfo) {
1032 if (hmm_vma_walk->pmdlocked) {
1033 spin_unlock(hmm_vma_walk->ptl);
1034 hmm_vma_walk->pmdlocked = false;
1035 }
1036 return r;
1037 }
1038 }
1039
1040 r = hmm_vma_handle_migrate_prepare_pmd(walk, pmdp, start, end, hmm_pfns);
1041
1042 if (hmm_vma_walk->pmdlocked) {
1043 spin_unlock(hmm_vma_walk->ptl);
1044 hmm_vma_walk->pmdlocked = false;
1045 }
1046
1047 if (r == -ENOENT) {
1048 r = hmm_vma_walk_split(pmdp, addr, walk);
1049 if (r) {
1050 /* Split not successful, skip */
1051 return hmm_pfns_fill(start, end, hmm_vma_walk, HMM_PFN_ERROR);
1052 }
1053
1054 /* Split successful or "again", reloop */
1055 hmm_vma_walk->last = addr;
1056 return -EBUSY;
1057 }
1058
1059 return r;
1060
1061 }
1062
1063 if (hmm_vma_walk->pmdlocked) {
1064 spin_unlock(hmm_vma_walk->ptl);
1065 hmm_vma_walk->pmdlocked = false;
1066 }
1067
1068 /*
1069 * We have handled all the valid cases above ie either none, migration,
1070 * huge or transparent huge. At this point either it is a valid pmd
1071 * entry pointing to pte directory or it is a bad pmd that will not
1072 * recover.
1073 */
1074 if (pmd_bad(pmd)) {
1075 if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0))
1076 return -EFAULT;
1077 return hmm_pfns_fill(start, end, hmm_vma_walk, HMM_PFN_ERROR);
1078 }
1079
1080 if (minfo) {
1081 ptep = pte_offset_map_lock(mm, pmdp, addr, &hmm_vma_walk->ptl);
1082 if (ptep)
1083 hmm_vma_walk->ptelocked = true;
1084 } else
1085 ptep = pte_offset_map(pmdp, addr);
1086 if (!ptep)
1087 goto again;
1088
1089 for (; addr < end; addr += PAGE_SIZE, ptep++, hmm_pfns++) {
1090
1091 r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, hmm_pfns);
1092 if (r) {
1093 /* hmm_vma_handle_pte() did pte_unmap() / pte_unmap_unlock */
1094 return r;
1095 }
1096
1097 r = hmm_vma_handle_migrate_prepare(walk, pmdp, ptep, addr, hmm_pfns);
1098 if (r == -EAGAIN) {
1099 HMM_ASSERT_UNLOCKED(hmm_vma_walk);
1100 goto again;
1101 }
1102 if (r) {
1103 hmm_pfns_fill(addr, end, hmm_vma_walk, HMM_PFN_ERROR);
1104 break;
1105 }
1106 }
1107
1108 if (hmm_vma_walk->ptelocked) {
1109 pte_unmap_unlock(ptep - 1, hmm_vma_walk->ptl);
1110 hmm_vma_walk->ptelocked = false;
1111 } else
1112 pte_unmap(ptep - 1);
1113
1114 return 0;
1115 }
1116
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
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