On Thu, Nov 10, 2022 at 01:35:47PM -0600, Bjorn Helgaas wrote: > Hi Wei, > > I can't quite parse this. Is the problem that you had some virtio I/O > in progress, you wrote "0" to /sys/.../sriov_numvfs, and the virtio > I/O operation hangs? I think so. I also think that just attempting to remove the module or to unbind the driver from it will have the same effect. > Is there any indication to the user, e.g., softlockup oops? > > More questions below. > > On Tue, Nov 08, 2022 at 04:52:16AM +0000, Wei Gong wrote: > > > according to sriov's protocol specification vendor_id and > > device_id field in all VFs return FFFFh when read > > so when vf devs is in the pci_device_is_present,it will be > > misjudged as surprise removeal > > > > when io is issued on the vf, normally disable virtio_blk vf > > devs,at this time the disable opration will hang. and virtio > > blk dev io hang. > > > > task:bash state:D stack: 0 pid: 1773 ppid: 1241 flags:0x00004002 > > Call Trace: > > <TASK> > > __schedule+0x2ee/0x900 > > schedule+0x4f/0xc0 > > blk_mq_freeze_queue_wait+0x69/0xa0 > > ? wait_woken+0x80/0x80 > > blk_mq_freeze_queue+0x1b/0x20 > > blk_cleanup_queue+0x3d/0xd0 > > virtblk_remove+0x3c/0xb0 [virtio_blk] > > virtio_dev_remove+0x4b/0x80 > > device_release_driver_internal+0x103/0x1d0 > > device_release_driver+0x12/0x20 > > bus_remove_device+0xe1/0x150 > > device_del+0x192/0x3f0 > > device_unregister+0x1b/0x60 > > unregister_virtio_device+0x18/0x30 > > virtio_pci_remove+0x41/0x80 > > pci_device_remove+0x3e/0xb0 > > device_release_driver_internal+0x103/0x1d0 > > device_release_driver+0x12/0x20 > > pci_stop_bus_device+0x79/0xa0 > > pci_stop_and_remove_bus_device+0x13/0x20 > > pci_iov_remove_virtfn+0xc5/0x130 > > ? pci_get_device+0x4a/0x60 > > sriov_disable+0x33/0xf0 > > pci_disable_sriov+0x26/0x30 > > virtio_pci_sriov_configure+0x6f/0xa0 > > sriov_numvfs_store+0x104/0x140 > > dev_attr_store+0x17/0x30 > > sysfs_kf_write+0x3e/0x50 > > kernfs_fop_write_iter+0x138/0x1c0 > > new_sync_write+0x117/0x1b0 > > vfs_write+0x185/0x250 > > ksys_write+0x67/0xe0 > > __x64_sys_write+0x1a/0x20 > > do_syscall_64+0x61/0xb0 > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > RIP: 0033:0x7f21bd1f3ba4 > > RSP: 002b:00007ffd34a24188 EFLAGS: 00000202 ORIG_RAX: 0000000000000001 > > RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f21bd1f3ba4 > > RDX: 0000000000000002 RSI: 0000560305040800 RDI: 0000000000000001 > > RBP: 0000560305040800 R08: 000056030503fd50 R09: 0000000000000073 > > R10: 00000000ffffffff R11: 0000000000000202 R12: 0000000000000002 > > R13: 00007f21bd2de760 R14: 00007f21bd2da5e0 R15: 00007f21bd2d99e0 > > > > when virtio_blk is performing io, as long as there two stages of: > > 1. dispatch io. queue_usage_counter++; > > 2. io is completed after receiving the interrupt. queue_usage_counter--; > > > > disable virtio_blk vfs: > > if(!pci_device_is_present(pci_dev)) > > virtio_break_device(&vp_dev->vdev); > > virtqueue for vf devs will be marked broken. > > the interrupt notification io is end. Since it is judged that the > > virtqueue has been marked as broken, the completed io will not be > > performed. > > So queue_usage_counter will not be cleared. > > when the disk is removed at the same time, the queue will be frozen, > > and you must wait for the queue_usage_counter to be cleared. > > Therefore, it leads to the removeal of hang. > > I want to follow along in the code, but I need some hints. > > "queue_usage_counter" looks like it's supposed to be a symbol, but I > can't find it. I think it refers to q->q_usage_counter in blk core. > Where (which function) is the I/O dispatched and queue_usage_counter > incremented? Where is queue_usage_counter decremented? > > Prior to this change pci_device_is_present(VF) returned "false" > (because the VF Vendor ID is 0xffff); after the change it will return > "true" (because it will look at the PF Vendor ID instead). > > Previously virtio_pci_remove() called virtio_break_device(). I guess > that meant the virtio I/O operation will never be completed? > > But if we don't call virtio_break_device(), the virtio I/O operation > *will* be completed? > > Bjorn It's completed anyway - nothing special happened at the device level - but driver does not detect it. Calling virtio_break_device will mark all queues as broken, as a result attempts to check whether operation completed will return false. This probably means we need to work on handling surprise removal better in virtio blk - since it looks like actual suprise removal will hang too. But that I think is a separate issue. -- MST
