Re: [PATCH] igb_uio: stop device when closing /dev/uioX

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 3/30/2017 9:22 PM, Thomas Monjalon wrote:
> 2016-12-02 16:45, Jianfeng Tan:
>> Depends-on: http://dpdk.org/dev/patchwork/patch/17493/
> 
> The above patch is marked as rejected.
> Do we want to reject also this patch?

Above patch rejected because it may have backward compatibility issues
with the older DPDK (1.8 and older if I remember correct) with newer
kernels.

Plan was checking if this patch can be updated to remove dependency, and
if not accepting above patch.

But as far as I can see not worked on it. We may drop this if Jianfeng
don't have any plan to work on it.

> 
>> When a DPDK application grab a PCI device, device and driver work
>> together to Rx/Tx packets. If the DPDK app crashes or gets killed,
>> there's no chance for DPDK driver to stop the device, which means
>> rte_eth_dev_stop() will not be called.
>>
>> This could result in problems. In virtio's case, the device (the
>> vhost backend), will keep working. If packets come, the vhost will
>> copy them into the vring, which is negotiated with the previous DPDK
>> app. But the resources, especially hugepages, are recycled by VM
>> kernel. What's worse, the memory could be allocated for other usage,
>> and re-written. This leads to an uncertain situation. Like this post
>> has reported, https://bugs.launchpad.net/qemu/+bug/1558175, QEMU's
>> vhost finds out wrong value, and exits the whole QEMU process.
>>
>> To make it right, we need to restart (or reset) the device and make
>> the device go into the initial state, when uio-generic or igb_uio
>> recycles the PCI device. There's a chance in uio framework to disable
>> devices when /dev/uioX gets closed. Here we enable the pci device
>> in open() hook and disable it in release() hook.
>>
>> However, if device is not enabled in probe() phase any more, we can
>> not register irq in probe() through uio_register_device(). To address
>> that, we invoke request_irq() to register callback directly.
>>
>> Similar change needs to be done in uio-generic driver. And vfio-pci
>> seems to have done that already.
>>
>> Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
>