From: Yifan Zhang yifan1.zhang@amd.com
[ Upstream commit 45da20e00d5da842e17dfc633072b127504f0d0e ]
current switch partition only check if kfd_processes_table is empty. kfd_prcesses_table entry is deleted in kfd_process_notifier_release, but kfd_process tear down is in kfd_process_wq_release.
consider two processes:
Process A (workqueue) -> kfd_process_wq_release -> Access kfd_node member Process B switch partition -> amdgpu_xcp_pre_partition_switch -> amdgpu_amdkfd_device_fini_sw -> kfd_node tear down.
Process A and B may trigger a race as shown in dmesg log.
This patch is to resolve the race by adding an atomic kfd_process counter kfd_processes_count, it increment as create kfd process, decrement as finish kfd_process_wq_release.
v2: Put kfd_processes_count per kfd_dev, move decrement to kfd_process_destroy_pdds and bug fix. (Philip Yang)
[3966658.307702] divide error: 0000 [#1] SMP NOPTI [3966658.350818] i10nm_edac [3966658.356318] CPU: 124 PID: 38435 Comm: kworker/124:0 Kdump: loaded Tainted [3966658.356890] Workqueue: kfd_process_wq kfd_process_wq_release [amdgpu] [3966658.362839] nfit [3966658.366457] RIP: 0010:kfd_get_num_sdma_engines+0x17/0x40 [amdgpu] [3966658.366460] Code: 00 00 e9 ac 81 02 00 66 66 2e 0f 1f 84 00 00 00 00 00 90 0f 1f 44 00 00 48 8b 4f 08 48 8b b7 00 01 00 00 8b 81 58 26 03 00 99 <f7> be b8 01 00 00 80 b9 70 2e 00 00 00 74 0b 83 f8 02 ba 02 00 00 [3966658.380967] x86_pkg_temp_thermal [3966658.391529] RSP: 0018:ffffc900a0edfdd8 EFLAGS: 00010246 [3966658.391531] RAX: 0000000000000008 RBX: ffff8974e593b800 RCX: ffff888645900000 [3966658.391531] RDX: 0000000000000000 RSI: ffff888129154400 RDI: ffff888129151c00 [3966658.391532] RBP: ffff8883ad79d400 R08: 0000000000000000 R09: ffff8890d2750af4 [3966658.391532] R10: 0000000000000018 R11: 0000000000000018 R12: 0000000000000000 [3966658.391533] R13: ffff8883ad79d400 R14: ffffe87ff662ba00 R15: ffff8974e593b800 [3966658.391533] FS: 0000000000000000(0000) GS:ffff88fe7f600000(0000) knlGS:0000000000000000 [3966658.391534] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [3966658.391534] CR2: 0000000000d71000 CR3: 000000dd0e970004 CR4: 0000000002770ee0 [3966658.391535] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [3966658.391535] DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400 [3966658.391536] PKRU: 55555554 [3966658.391536] Call Trace: [3966658.391674] deallocate_sdma_queue+0x38/0xa0 [amdgpu] [3966658.391762] process_termination_cpsch+0x1ed/0x480 [amdgpu] [3966658.399754] intel_powerclamp [3966658.402831] kfd_process_dequeue_from_all_devices+0x5b/0xc0 [amdgpu] [3966658.402908] kfd_process_wq_release+0x1a/0x1a0 [amdgpu] [3966658.410516] coretemp [3966658.434016] process_one_work+0x1ad/0x380 [3966658.434021] worker_thread+0x49/0x310 [3966658.438963] kvm_intel [3966658.446041] ? process_one_work+0x380/0x380 [3966658.446045] kthread+0x118/0x140 [3966658.446047] ? __kthread_bind_mask+0x60/0x60 [3966658.446050] ret_from_fork+0x1f/0x30 [3966658.446053] Modules linked in: kpatch_20765354(OEK) [3966658.455310] kvm [3966658.464534] mptcp_diag xsk_diag raw_diag unix_diag af_packet_diag netlink_diag udp_diag act_pedit act_mirred act_vlan cls_flower kpatch_21951273(OEK) kpatch_18424469(OEK) kpatch_19749756(OEK) [3966658.473462] idxd_mdev [3966658.482306] kpatch_17971294(OEK) sch_ingress xt_conntrack amdgpu(OE) amdxcp(OE) amddrm_buddy(OE) amd_sched(OE) amdttm(OE) amdkcl(OE) intel_ifs iptable_mangle tcm_loop target_core_pscsi tcp_diag target_core_file inet_diag target_core_iblock target_core_user target_core_mod coldpgs kpatch_18383292(OEK) ip6table_nat ip6table_filter ip6_tables ip_set_hash_ipportip ip_set_hash_ipportnet ip_set_hash_ipport ip_set_bitmap_port xt_comment iptable_nat nf_nat iptable_filter ip_tables ip_set ip_vs_sh ip_vs_wrr ip_vs_rr ip_vs nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 sn_core_odd(OE) i40e overlay binfmt_misc tun bonding(OE) aisqos(OE) aisqos_hotfixes(OE) rfkill uio_pci_generic uio cuse fuse nf_tables nfnetlink intel_rapl_msr intel_rapl_common intel_uncore_frequency intel_uncore_frequency_common i10nm_edac nfit x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm idxd_mdev [3966658.491237] vfio_pci [3966658.501196] vfio_pci vfio_virqfd mdev vfio_iommu_type1 vfio iax_crypto intel_pmt_telemetry iTCO_wdt intel_pmt_class iTCO_vendor_support irqbypass crct10dif_pclmul crc32_pclmul ghash_clmulni_intel rapl intel_cstate snd_hda_intel snd_intel_dspcfg snd_hda_codec snd_hda_core snd_hwdep snd_seq [3966658.508537] vfio_virqfd [3966658.517569] snd_seq_device ipmi_ssif isst_if_mbox_pci isst_if_mmio pcspkr snd_pcm idxd intel_uncore ses isst_if_common intel_vsec idxd_bus enclosure snd_timer mei_me snd i2c_i801 i2c_smbus mei i2c_ismt soundcore joydev acpi_ipmi ipmi_si ipmi_devintf ipmi_msghandler acpi_power_meter acpi_pad vfat fat [3966658.526851] mdev [3966658.536096] nfsd auth_rpcgss nfs_acl lockd grace slb_vtoa(OE) sunrpc dm_mod hookers mlx5_ib(OE) ast i2c_algo_bit drm_vram_helper drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops drm_ttm_helper ttm mlx5_core(OE) mlxfw(OE) [3966658.540381] vfio_iommu_type1 [3966658.544341] nvme mpt3sas tls drm nvme_core pci_hyperv_intf raid_class psample libcrc32c crc32c_intel mlxdevm(OE) i2c_core [3966658.551254] vfio [3966658.558742] scsi_transport_sas wmi pinctrl_emmitsburg sd_mod t10_pi sg ahci libahci libata rdma_ucm(OE) ib_uverbs(OE) rdma_cm(OE) iw_cm(OE) ib_cm(OE) ib_umad(OE) ib_core(OE) ib_ucm(OE) mlx_compat(OE) [3966658.563004] iax_crypto [3966658.570988] [last unloaded: diagnose] [3966658.571027] ---[ end trace cc9dbb180f9ae537 ]---
Signed-off-by: Yifan Zhang yifan1.zhang@amd.com Reviewed-by: Philip.YangPhilip.Yang@amd.com Signed-off-by: Alex Deucher alexander.deucher@amd.com Signed-off-by: Sasha Levin sashal@kernel.org ---
LLM Generated explanations, may be completely bogus:
YES - The crash the commit describes is real: when `kfd_process_notifier_release` removes a process from `kfd_processes_table`, the subsequent `kfd_process_wq_release` can still touch `kfd_node` while `kgd2kfd_check_and_lock_kfd` allows a partition switch to proceed, tearing the device down and triggering the reported divide error in `kfd_get_num_sdma_engines`. The regression was introduced when commit `96f75f9594466f` relaxed the partition switch guard to rely only on the hash table; the new trace shows we now have a use-after-free window. - The fix is tight and well scoped: it adds a per-device atomic counter at `drivers/gpu/drm/amd/amdkfd/kfd_priv.h:386` and initializes it in `kgd2kfd_probe` (`drivers/gpu/drm/amd/amdkfd/kfd_device.c:498`). `kgd2kfd_check_and_lock_kfd` now refuses partition switches while that counter is non-zero (`drivers/gpu/drm/amd/amdkfd/kfd_device.c:1495-1503`), preventing the race. - The counter is balanced across process lifecycle: it increments whenever a process device descriptor is created (`drivers/gpu/drm/amd/amdkfd/kfd_process.c:1644-1654`) and decrements when the descriptor is destroyed in the workqueue cleanup (`drivers/gpu/drm/amd/amdkfd/kfd_process.c:1085-1093`). Because `kfd_process_destroy_pdds` zeroes `p->n_pdds` after the loop, double decrements are prevented. - Side effects are minimal: the patch touches only amdkfd code, introduces no API/ABI changes, and relies on existing synchronization (`kfd_processes_mutex` and atomics). The new counter simply gatekeeps the existing teardown path, so regression risk is low. No follow-up fixes are required. - For stable backports, ensure the base tree already contains the compute-partition switch support from `96f75f9594466f`; earlier kernels that never allowed switching with live processes don’t hit this race and wouldn’t benefit. On trees with that support, this change cleanly applies and prevents a hard crash, making it an excellent stable candidate.
Next step: cherry-pick 45da20e00d5da842e17dfc633072b127504f0d0e onto the relevant stable branches and run the usual amdgpu/amdkfd partition- switch regression tests.
drivers/gpu/drm/amd/amdkfd/kfd_device.c | 10 ++++++++++ drivers/gpu/drm/amd/amdkfd/kfd_priv.h | 2 ++ drivers/gpu/drm/amd/amdkfd/kfd_process.c | 4 ++++ 3 files changed, 16 insertions(+)
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_device.c b/drivers/gpu/drm/amd/amdkfd/kfd_device.c index 051a00152b089..e9cfb80bd4366 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_device.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_device.c @@ -495,6 +495,7 @@ struct kfd_dev *kgd2kfd_probe(struct amdgpu_device *adev, bool vf) mutex_init(&kfd->doorbell_mutex);
ida_init(&kfd->doorbell_ida); + atomic_set(&kfd->kfd_processes_count, 0);
return kfd; } @@ -1493,6 +1494,15 @@ int kgd2kfd_check_and_lock_kfd(struct kfd_dev *kfd)
mutex_lock(&kfd_processes_mutex);
+ /* kfd_processes_count is per kfd_dev, return -EBUSY without + * further check + */ + if (!!atomic_read(&kfd->kfd_processes_count)) { + pr_debug("process_wq_release not finished\n"); + r = -EBUSY; + goto out; + } + if (hash_empty(kfd_processes_table) && !kfd_is_locked(kfd)) goto out;
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h index d01ef5ac07666..70ef051511bb1 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h +++ b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h @@ -382,6 +382,8 @@ struct kfd_dev {
/* for dynamic partitioning */ int kfd_dev_lock; + + atomic_t kfd_processes_count; };
enum kfd_mempool { diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c index 5be28c6c4f6aa..ddfe30c13e9d6 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c @@ -1088,6 +1088,8 @@ static void kfd_process_destroy_pdds(struct kfd_process *p) pdd->runtime_inuse = false; }
+ atomic_dec(&pdd->dev->kfd->kfd_processes_count); + kfree(pdd); p->pdds[i] = NULL; } @@ -1649,6 +1651,8 @@ struct kfd_process_device *kfd_create_process_device_data(struct kfd_node *dev, /* Init idr used for memory handle translation */ idr_init(&pdd->alloc_idr);
+ atomic_inc(&dev->kfd->kfd_processes_count); + return pdd; }