kernel/linux.git/lib/test_hmm.c, branch v7.1-rc5

lib: test_hmm: implement a device release method

2026-04-18T07:10:52+00:00

Unloading the HMM test module produces the following warning: [ 3782.224783] ------------[ cut here ]------------ [ 3782.226323] Device 'hmm_dmirror0' does not have a release() function, it is broken and must be fixed. See Documentation/core-api/kobject.rst. [ 3782.230570] WARNING: drivers/base/core.c:2567 at device_release+0x185/0x210, CPU#20: rmmod/1924 [ 3782.233949] Modules linked in: test_hmm(-) nvidia_uvm(O) nvidia(O) [ 3782.236321] CPU: 20 UID: 0 PID: 1924 Comm: rmmod Tainted: G O 7.0.0-rc1+ #374 PREEMPT(full) [ 3782.240226] Tainted: [O]=OOT_MODULE [ 3782.241639] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014 [ 3782.246193] RIP: 0010:device_release+0x185/0x210 [ 3782.247860] Code: 00 00 fc ff df 48 8d 7b 50 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 86 00 00 00 48 8b 73 50 48 85 f6 74 11 48 8d 3d db 25 29 03 <67> 48 0f b9 3a e9 0d ff ff ff 48 b8 00 00 00 00 00 fc ff df 48 89 [ 3782.254211] RSP: 0018:ffff888126577d98 EFLAGS: 00010246 [ 3782.256054] RAX: dffffc0000000000 RBX: ffffffffc2b70310 RCX: ffffffff8fe61ba1 [ 3782.258512] RDX: 1ffffffff856e062 RSI: ffff88811341eea0 RDI: ffffffff91bbacb0 [ 3782.261041] RBP: ffff888111475000 R08: 0000000000000001 R09: fffffbfff856e069 [ 3782.263471] R10: ffffffffc2b7034b R11: 00000000ffffffff R12: 0000000000000000 [ 3782.265983] R13: dffffc0000000000 R14: ffff88811341eea0 R15: 0000000000000000 [ 3782.268443] FS: 00007fd5a3689040(0000) GS:ffff88842c8d0000(0000) knlGS:0000000000000000 [ 3782.271236] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 3782.273251] CR2: 00007fd5a36d2c10 CR3: 00000001242b8000 CR4: 00000000000006f0 [ 3782.275362] Call Trace: [ 3782.276071] [ 3782.276678] kobject_put+0x146/0x270 [ 3782.277731] hmm_dmirror_exit+0x7a/0x130 [test_hmm] [ 3782.279135] __do_sys_delete_module+0x341/0x510 [ 3782.280438] ? module_flags+0x300/0x300 [ 3782.281547] do_syscall_64+0x111/0x670 [ 3782.282620] entry_SYSCALL_64_after_hwframe+0x4b/0x53 [ 3782.284091] RIP: 0033:0x7fd5a3793b37 [ 3782.285303] Code: 73 01 c3 48 8b 0d c9 82 0c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 b0 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 99 82 0c 00 f7 d8 64 89 01 48 [ 3782.290708] RSP: 002b:00007ffd68b7dc68 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0 [ 3782.292817] RAX: ffffffffffffffda RBX: 000055e3c0d1c770 RCX: 00007fd5a3793b37 [ 3782.294735] RDX: 0000000000000000 RSI: 0000000000000800 RDI: 000055e3c0d1c7d8 [ 3782.296661] RBP: 0000000000000000 R08: 1999999999999999 R09: 0000000000000000 [ 3782.298622] R10: 00007fd5a3806ac0 R11: 0000000000000206 R12: 00007ffd68b7deb0 [ 3782.300576] R13: 00007ffd68b7e781 R14: 000055e3c0d1b2a0 R15: 00007ffd68b7deb8 [ 3782.301963] [ 3782.302371] irq event stamp: 5019 [ 3782.302987] hardirqs last enabled at (5027): [] __up_console_sem+0x52/0x60 [ 3782.304507] hardirqs last disabled at (5036): [] __up_console_sem+0x37/0x60 [ 3782.306086] softirqs last enabled at (4940): [] __irq_exit_rcu+0xc0/0xf0 [ 3782.307567] softirqs last disabled at (4929): [] __irq_exit_rcu+0xc0/0xf0 [ 3782.309105] ---[ end trace 0000000000000000 ]--- This is because the test module doesn't have a device.release method. In this case one probably isn't needed for correctness - the device structs are in a static array so don't need freeing when the final reference goes away. However some device state is freed on exit, so to ensure this happens at the right time and to silence the warning move the deinitialisation to a release method and assign that as the device release callback. Whilst here also fix a minor error handling bug where cdev_device_del() wasn't being called if allocation failed. Link: https://lore.kernel.org/20260331063445.3551404-4-apopple@nvidia.com Fixes: 6a760f58c792 ("mm/hmm/test: use char dev with struct device to get device node") Signed-off-by: Alistair Popple Acked-by: Balbir Singh Tested-by: Zenghui Yu (Huawei) Cc: David Hildenbrand Cc: Jason Gunthorpe Cc: Leon Romanovsky Cc: Liam Howlett Cc: Lorenzo Stoakes (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Matthew Brost Cc: Signed-off-by: Andrew Morton

lib: test_hmm: evict device pages on file close to avoid use-after-free

2026-04-18T07:10:52+00:00

Patch series "Minor hmm_test fixes and cleanups". Two bugfixes a cleanup for the HMM kernel selftests. These were mostly reported by Zenghui Yu with special thanks to Lorenzo for analysing and pointing out the problems. This patch (of 3): When dmirror_fops_release() is called it frees the dmirror struct but doesn't migrate device private pages back to system memory first. This leaves those pages with a dangling zone_device_data pointer to the freed dmirror. If a subsequent fault occurs on those pages (eg. during coredump) the dmirror_devmem_fault() callback dereferences the stale pointer causing a kernel panic. This was reported [1] when running mm/ksft_hmm.sh on arm64, where a test failure triggered SIGABRT and the resulting coredump walked the VMAs faulting in the stale device private pages. Fix this by calling dmirror_device_evict_chunk() for each devmem chunk in dmirror_fops_release() to migrate all device private pages back to system memory before freeing the dmirror struct. The function is moved earlier in the file to avoid a forward declaration. Link: https://lore.kernel.org/20260331063445.3551404-1-apopple@nvidia.com Link: https://lore.kernel.org/20260331063445.3551404-2-apopple@nvidia.com Fixes: b2ef9f5a5cb3 ("mm/hmm/test: add selftest driver for HMM") Signed-off-by: Alistair Popple Reported-by: Zenghui Yu Closes: https://lore.kernel.org/linux-mm/8bd0396a-8997-4d2e-a13f-5aac033083d7@linux.dev/ Reviewed-by: Balbir Singh Tested-by: Zenghui Yu Cc: David Hildenbrand Cc: Jason Gunthorpe Cc: Leon Romanovsky Cc: Liam Howlett Cc: Lorenzo Stoakes (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Zenghui Yu Cc: Matthew Brost Cc: Signed-off-by: Andrew Morton

Convert 'alloc_obj' family to use the new default GFP_KERNEL argument

2026-02-22T01:09:51+00:00

This was done entirely with mindless brute force, using git grep -l '\

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook

mm/zone_device: reinitialize large zone device private folios

2026-01-27T03:03:48+00:00

Reinitialize metadata for large zone device private folios in zone_device_page_init prior to creating a higher-order zone device private folio. This step is necessary when the folio's order changes dynamically between zone_device_page_init calls to avoid building a corrupt folio. As part of the metadata reinitialization, the dev_pagemap must be passed in from the caller because the pgmap stored in the folio page may have been overwritten with a compound head. Without this fix, individual pages could have invalid pgmap fields and flags (with PG_locked being notably problematic) due to prior different order allocations, which can, and will, result in kernel crashes. Link: https://lkml.kernel.org/r/20260116111325.1736137-2-francois.dugast@intel.com Fixes: d245f9b4ab80 ("mm/zone_device: support large zone device private folios") Signed-off-by: Matthew Brost Signed-off-by: Francois Dugast Acked-by: Felix Kuehling Reviewed-by: Balbir Singh Acked-by: Vlastimil Babka Cc: Zi Yan Cc: Alistair Popple Cc: Madhavan Srinivasan Cc: Nicholas Piggin Cc: Michael Ellerman Cc: "Christophe Leroy (CS GROUP)" Cc: Alex Deucher Cc: "Christian König" Cc: David Airlie Cc: Simona Vetter Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Thomas Zimmermann Cc: Lyude Paul Cc: Danilo Krummrich Cc: David Hildenbrand Cc: Oscar Salvador Cc: Andrew Morton Cc: Jason Gunthorpe Cc: Leon Romanovsky Cc: Lorenzo Stoakes Cc: Liam R. Howlett Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Michal Hocko Signed-off-by: Andrew Morton

mm/hmm/test: fix error handling in dmirror_device_init

2025-11-24T23:08:50+00:00

dmirror_device_init() calls device_initialize() which sets the device reference count to 1, but fails to call put_device() when error occurs after dev_set_name() or cdev_device_add() failures. This results in memory leaks of struct device objects. Additionally, dmirror_device_remove() lacks the final put_device() call to properly release the device reference. Found by code review. Link: https://lkml.kernel.org/r/20251108115346.6368-1-make24@iscas.ac.cn Fixes: 6a760f58c792 ("mm/hmm/test: use char dev with struct device to get device node") Signed-off-by: Ma Ke Cc: Haoxiang Li Cc: Jason Gunthorpe Cc: John Hubbard Cc: Leon Romanovsky Cc: Mika Penttilä Signed-off-by: Andrew Morton

lib/test_hmm: add large page allocation failure testing

2025-11-24T23:08:48+00:00

Add HMM_DMIRROR_FLAG_FAIL_ALLOC flag to simulate large page allocation failures, enabling testing of split migration code paths. This test flag allows validation of the fallback behavior when destination device cannot allocate compound pages. This is useful for testing the split migration functionality. Link: https://lkml.kernel.org/r/20251001065707.920170-13-balbirs@nvidia.com Signed-off-by: Balbir Singh Cc: David Hildenbrand Cc: Zi Yan Cc: Joshua Hahn Cc: Rakie Kim Cc: Byungchul Park Cc: Gregory Price Cc: Ying Huang Cc: Alistair Popple Cc: Oscar Salvador Cc: Lorenzo Stoakes Cc: Baolin Wang Cc: "Liam R. Howlett" Cc: Nico Pache Cc: Ryan Roberts Cc: Dev Jain Cc: Barry Song Cc: Lyude Paul Cc: Danilo Krummrich Cc: David Airlie Cc: Simona Vetter Cc: Ralph Campbell Cc: Mika Penttilä Cc: Matthew Brost Cc: Francois Dugast Signed-off-by: Andrew Morton

mm/migrate_device: add THP splitting during migration

2025-11-24T23:08:48+00:00

Implement migrate_vma_split_pages() to handle THP splitting during the migration process when destination cannot allocate compound pages. This addresses the common scenario where migrate_vma_setup() succeeds with MIGRATE_PFN_COMPOUND pages, but the destination device cannot allocate large pages during the migration phase. Key changes: - migrate_vma_split_pages(): Split already-isolated pages during migration - Enhanced folio_split() and __split_unmapped_folio() with isolated parameter to avoid redundant unmap/remap operations This provides a fallback mechansim to ensure migration succeeds even when large page allocation fails at the destination. [matthew.brost@intel.com: add THP splitting during migration] Link: https://lkml.kernel.org/r/20251120230825.181072-2-matthew.brost@intel.com Link: https://lkml.kernel.org/r/20251001065707.920170-12-balbirs@nvidia.com Signed-off-by: Balbir Singh Signed-off-by: Matthew Brost Cc: David Hildenbrand Cc: Zi Yan Cc: Joshua Hahn Cc: Rakie Kim Cc: Byungchul Park Cc: Gregory Price Cc: Ying Huang Cc: Alistair Popple Cc: Oscar Salvador Cc: Lorenzo Stoakes Cc: Baolin Wang Cc: "Liam R. Howlett" Cc: Nico Pache Cc: Ryan Roberts Cc: Dev Jain Cc: Barry Song Cc: Lyude Paul Cc: Danilo Krummrich Cc: David Airlie Cc: Simona Vetter Cc: Ralph Campbell Cc: Mika Penttilä Cc: Francois Dugast Signed-off-by: Andrew Morton

mm/memremap: add driver callback support for folio splitting

2025-11-24T23:08:48+00:00

When a zone device page is split (via huge pmd folio split). The driver callback for folio_split is invoked to let the device driver know that the folio size has been split into a smaller order. Provide a default implementation for drivers that do not provide this callback that copies the pgmap and mapping fields for the split folios. Update the HMM test driver to handle the split. Link: https://lkml.kernel.org/r/20251001065707.920170-11-balbirs@nvidia.com Signed-off-by: Balbir Singh Cc: David Hildenbrand Cc: Zi Yan Cc: Joshua Hahn Cc: Rakie Kim Cc: Byungchul Park Cc: Gregory Price Cc: Ying Huang Cc: Alistair Popple Cc: Oscar Salvador Cc: Lorenzo Stoakes Cc: Baolin Wang Cc: "Liam R. Howlett" Cc: Nico Pache Cc: Ryan Roberts Cc: Dev Jain Cc: Barry Song Cc: Lyude Paul Cc: Danilo Krummrich Cc: David Airlie Cc: Simona Vetter Cc: Ralph Campbell Cc: Mika Penttilä Cc: Matthew Brost Cc: Francois Dugast Signed-off-by: Andrew Morton

lib/test_hmm: add zone device private THP test infrastructure

2025-11-24T23:08:48+00:00

Enhance the hmm test driver (lib/test_hmm) with support for THP pages. A new pool of free_folios() has now been added to the dmirror device, which can be allocated when a request for a THP zone device private page is made. Add compound page awareness to the allocation function during normal migration and fault based migration. These routines also copy folio_nr_pages() when moving data between system memory and device memory. args.src and args.dst used to hold migration entries are now dynamically allocated (as they need to hold HPAGE_PMD_NR entries or more). Split and migrate support will be added in future patches in this series. Link: https://lkml.kernel.org/r/20251001065707.920170-10-balbirs@nvidia.com Signed-off-by: Balbir Singh Cc: David Hildenbrand Cc: Zi Yan Cc: Joshua Hahn Cc: Rakie Kim Cc: Byungchul Park Cc: Gregory Price Cc: Ying Huang Cc: Alistair Popple Cc: Oscar Salvador Cc: Lorenzo Stoakes Cc: Baolin Wang Cc: "Liam R. Howlett" Cc: Nico Pache Cc: Ryan Roberts Cc: Dev Jain Cc: Barry Song Cc: Lyude Paul Cc: Danilo Krummrich Cc: David Airlie Cc: Simona Vetter Cc: Ralph Campbell Cc: Mika Penttilä Cc: Matthew Brost Cc: Francois Dugast Signed-off-by: Andrew Morton