Re: [PATCH] doc: add known igb_uio device hot-unplug issue

[Jeff Guo <jia.guo@intel.com>]

On 11/21/2018 2:02 AM, Stephen Hemminger wrote:
> On Tue, 20 Nov 2018 23:09:31 +0800
> Jeff Guo <jia.guo@intel.com> wrote:
>
>> When device has been bound to igb_uio driver and application is running,
>> hot-unplugging the device may cause kernel crash.
>>
>> Signed-off-by: Jeff Guo <jia.guo@intel.com>
>> ---
>>   doc/guides/rel_notes/known_issues.rst | 21 +++++++++++++++++++++
>>   1 file changed, 21 insertions(+)
>>
>> diff --git a/doc/guides/rel_notes/known_issues.rst b/doc/guides/rel_notes/known_issues.rst
>> index 95e4ce6..dfe0565 100644
>> --- a/doc/guides/rel_notes/known_issues.rst
>> +++ b/doc/guides/rel_notes/known_issues.rst
>> @@ -759,3 +759,24 @@ Netvsc driver and application restart
>>   
>>   **Driver/Module**:
>>      ``uio_hv_generic`` module.
>> +
>> +
>> +kernel crash when hot-unplug igb_uio device while DPDK application is running
>> +-----------------------------------------------------------------------------
>> +
>> +**Description**:
>> +   When device has been bound to igb_uio driver and application is running, hot-unplugging
>> +   the device may cause kernel crash.
>> +
>> +**Reason**:
>> +   When device is hot-unplugged, igb_uio driver will be removed which will destroy uio resources.
>> +   Later trying to access any uio resource will cause kernel crash.
>> +
>> +**Resolution/Workaround**:
>> +   If using DPDK for PCI HW hot-unplug, prefer to bind device with VFIO instead of IGB_UIO.
>> +
>> +**Affected Environment/Platform**:
>> +    ALL.
>> +
>> +**Driver/Module**:
>> +   ``igb_uio`` module.
> Surely this is fixable. What is the back trace in the kernel? How can it be reproduced with some
> common hardware (or hypervisor).  Will it happen with KVM?

I think the final fix should be at uio_module in the linux kernel,  and 
workaround could be in user space and igb_uio kernel driver if there is 
a better one. So that is why we need a document here.


you could reference the back trace as below.

[ 1078.006709] RIP: 0010:uio_write+0x2e/0xc0 [uio]

[ 1078.006727] Call Trace: [ 1078.006765]

  __vfs_write+0x18/0x40 [ 1078.006768]

  vfs_write+0xb8/0x1b0 [ 1078.006770]

  SyS_write+0x55/0xc0 [ 1078.006791]

  entry_SYSCALL_64_fastpath+0x1e/0xad [ 1078.006793]

RIP: 0033:0x7f75a10224bd


you could check the whole info  at below link which i have attach.

http://patches.dpdk.org/patch/47923/


The system env:

Host kernel: 4.17.0-041700rc1-generic

Vm kernel: Linux ubuntu 4.10.0-28-generic #32~16.04.2-Ubuntu.

QEMU emulator version: 2.5.0

DPDK: version: 18.11-rc4

NIC: ixgbe or i40e nic or other(igb_uio pci nic)

Reproduce step:

Host environment

1. Host: Bind port 0 to vfio-pci

    modprobe vfio_pci

./usertools/dpdk-devbind.py -b vfio-pci 81:10.0

2. start qemu scripts

taskset -c 12-21 qemu-system-x86_64 \

-enable-kvm -m 8192 -smp cores=10,sockets=1 -cpu host -name dpdk1-vm1 \

-monitor stdio \

-drive file=/home/vm/ubuntu-14.04.img \

-device vfio-pci,host=0000:81:10.0,id=dev1 \

-netdev tap,id=ipvm1,ifname=tap5,script=/etc/qemu-ifup -device 
rtl8139,netdev=ipvm1,id=net0,mac=00:00:00:00:00:01 \

-localtime -vnc :2


VM environment

1. Bind port 0 to igb_uio

./usertools/dpdk-devbind.py --st

./usertools/dpdk-devbind.py -b igb_uio 00:03.0

2. Start testpmd and enable hotplug feature

./x86_64-native-linuxapp-gcc/app/testpmd -c f -n 4 -- -i --hot-plug

3. testpmd>set fwd txonly

4. testpmd>start

5. Qemu: remove device for unplug:

(qemu) device_del dev1

6.Qemu : add device for plug:

(qemu) device_add vfio-pci,host=0000:81:10.0,id=dev1

7. Bind port 0 to igb_uio：

./usertools/dpdk-devbind.py -b igb_uio 00:03.0

8. testpmd>stop

9. testpmd>port attach 0000: 00:03.0

10. testpmd>port start all

11. testpmd>start

12. Repeat 5 -- 12 until the kernel crash occur.