> From: Jason Wang <jasowang@xxxxxxxxxx> > Sent: Tuesday, June 18, 2024 9:18 AM > > On Mon, Jun 17, 2024 at 11:51 PM Dragos Tatulea <dtatulea@xxxxxxxxxx> > wrote: > > > > Hi, > > > > After commit ba168b52bf8e "mm: use rwsem assertion macros for > > mmap_lock") was submitted, we started getting a lot of the > > following warnings about a missing mmap write lock during VM boot: > > > > ------------[ cut here ]------------ > > WARNING: CPU: 1 PID: 58633 at include/linux/rwsem.h:85 > > track_pfn_remap+0x12b/0x130 > > Modules linked in: act_mirred act_skbedit vhost_vdpa cls_matchall > > nfnetlink_cttimeout act_gact cls_flower sch_ingress mlx5_vdpa vringh vdpa > > openvswitch nsh vhost_net vhost vhost_iotlb tap ip6table_mangle > ip6table_nat > > iptable_mangle nf_tables ip6table_filter ip6_tables xt_conntrack > xt_MASQUERADE > > nf_conntrack_netlink nfnetlink xt_addrtype iptable_nat nf_nat br_netfilter > > rpcsec_gss_krb5 auth_rpcgss oid_registry overlay rpcrdma rdma_ucm > ib_iser > > libiscsi ib_umad scsi_transport_iscsi ib_ipoib rdma_cm iw_cm ib_cm > mlx5_ib > > ib_uverbs ib_core fuse mlx5_core > > CPU: 1 PID: 58633 Comm: CPU 0/KVM Tainted: G W > > 6.10.0-rc1_for_upstream_min_debug_2024_05_29_17_06 #1 > > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS > > rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 > > RIP: 0010:track_pfn_remap+0x12b/0x130 > > Code: 48 83 c4 08 b8 ea ff ff ff 5b 5d 41 5c 41 5d c3 48 83 c4 08 48 89 ef 48 > > 89 f2 5b 31 c9 4c 89 c6 5d 41 5c 41 5d e9 f5 fb ff ff <0f> 0b eb 9b 90 0f 1f 44 > > 00 00 80 3d ac 59 96 01 00 74 01 c3 48 89 > > RSP: 0018:ffff888350f8b8e0 EFLAGS: 00010246 > > RAX: 0000000000000000 RBX: 0000000000001000 RCX: 0000000000000000 > > RDX: ffff8881080ca300 RSI: 0000000000001000 RDI: 0000000544003000 > > RBP: 0000000544003000 R08: ffff888106730a60 R09: 0000000000000000 > > R10: ffff888116eeff60 R11: 0000000000000000 R12: ffff888350f8b918 > > R13: ffff888149f99da8 R14: 0000000000001000 R15: 0000000000001000 > > FS: 00007f678d800700(0000) GS:ffff88852c880000(0000) > knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 00000000004e54f8 CR3: 0000000112290004 CR4: 0000000000372eb0 > > Call Trace: > > <TASK> > > ? __warn+0x78/0x110 > > ? track_pfn_remap+0x12b/0x130 > > ? report_bug+0x16d/0x180 > > ? handle_bug+0x3c/0x60 > > ? exc_invalid_op+0x14/0x70 > > ? asm_exc_invalid_op+0x16/0x20 > > ? track_pfn_remap+0x12b/0x130 > > remap_pfn_range+0x41/0xa0 > > vhost_vdpa_fault+0x6c/0xa0 [vhost_vdpa] > > __do_fault+0x2f/0xb0 > > __handle_mm_fault+0x13d3/0x2210 > > handle_mm_fault+0xb0/0x260 > > fixup_user_fault+0x77/0x170 > > hva_to_pfn+0x2c5/0x4b0 > > kvm_faultin_pfn+0xd7/0x510 > > kvm_tdp_page_fault+0x111/0x190 > > kvm_mmu_do_page_fault+0x105/0x230 > > kvm_mmu_page_fault+0x7d/0x620 > > ? vmx_deliver_interrupt+0x110/0x190 > > ? __apic_accept_irq+0x16c/0x270 > > ? vmx_vmexit+0x8d/0xc0 > > vmx_handle_exit+0x110/0x640 > > kvm_arch_vcpu_ioctl_run+0xdb0/0x1c20 > > kvm_vcpu_ioctl+0x263/0x6a0 > > ? futex_wake+0x81/0x180 > > __x64_sys_ioctl+0x4a7/0x9d0 > > ? __x64_sys_futex+0x73/0x1c0 > > ? kvm_on_user_return+0x86/0x90 > > do_syscall_64+0x4c/0x100 > > entry_SYSCALL_64_after_hwframe+0x4b/0x53 > > RIP: 0033:0x7f679186a17b > > Code: 0f 1e fa 48 8b 05 1d ad 0c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff > > c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 > > c3 48 8b 0d ed ac 0c 00 f7 d8 64 89 01 48 > > RSP: 002b:00007f678d7ff788 EFLAGS: 00000246 ORIG_RAX: > 0000000000000010 > > RAX: ffffffffffffffda RBX: 000000000000ae80 RCX: 00007f679186a17b > > RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000059 > > RBP: 000055da5ee22050 R08: 000055da44b28160 R09: 0000000000000000 > > R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000 > > R13: 000055da452b05e0 R14: 0000000000000001 R15: 0000000000000000 > > </TASK> > > ---[ end trace 0000000000000000 ]--- > > > > The warnings show up only when the vdpa page-per-vq option is used > (doorbell > > mapping to guest). > > > > The issue seems to have existed before, but was visible only with > CONFIG_LOCKDEP > > enabled. I tried finding if this was introduced in more recent kernels, but > > stopped after going as far back as 6.5: the issue was still visible there. > > > > The warning is triggered for the following call chain: > > vhost_vdpa_fault() > > -> remap_pfn_range() > > -> remap_pfn_range_notrack() > > -> vm_flags_set() > > -> vma_start_write() > > -> __is_vma_write_locked() > > -> mmap_assert_write_locked() > > > > > > I've been trying to follow how the mm write lock is dropped in the above > call > > chain or not taken at all. But I couldn't make much sense of it... > > I've also had a glance at vfio_pci_mmap_fault, it seems to do something > similar. > > > Any ideas of what could have gone wrong here? > > Adding Peter for more thought here. > vfio-side fix was just queued for rc4: https://lore.kernel.org/all/20240614155603.34567eb7.alex.williamson@xxxxxxxxxx/T/
