Re: [PATCH v4 0/2] Add VHOST PMD

[Tetsuya Mukawa <mukawa@igel.co.jp>]

On 2015/11/17 22:26, Yuanhan Liu wrote:
> On Fri, Nov 13, 2015 at 03:50:16PM +0900, Tetsuya Mukawa wrote:
>> On 2015/11/13 14:32, Yuanhan Liu wrote:
>>> On Fri, Nov 13, 2015 at 02:20:29PM +0900, Tetsuya Mukawa wrote:
>>>> The patch introduces a new PMD. This PMD is implemented as thin wrapper
>>>> of librte_vhost.
>>>>
>>>> * Known issue.
>>>> We may see issues while handling RESET_OWNER message.
>>>> These handlings are done in vhost library, so not a part of vhost PMD.
>>>> So far, we are waiting for QEMU fixing.
>>> Fix patches have already been applied. Please help test :)
>>>
>>> 	--yliu
>> Hi Yuanhan,
>>
>> It seems there might be an another issue related with "vq->callfd" in
>> vhost library.
>> We may miss something to handle the value correctly.
>>
>> Anyway, here are steps.
>> 1. Apply vhost PMD patch.
>> (I guess you don't need it to reproduce the issue, but to reproduce it,
>> using the PMD may be easy)
>> 2. Start testpmd on host with vhost-user PMD.
>> 3. Start QEMU with virtio-net device.
>> 4. Login QEMU.
>> 5. Bind the virtio-net device to igb_uio.
>> 6. Start testpmd in QEMU.
>> 7. Quit testmd in QEMU.
>> 8. Start testpmd again in QEMU.
>>
>> It seems when last command is executed, testpmd on host doesn't receive
>> SET_VRING_CALL message from QEMU.
>> Because of this, testpmd on host assumes virtio-net device is not ready.
>> (I made sure virtio_is_ready() was failed on host).
>>
>> According to QEMU source code, SET_VRING_KICK will be called when
>> virtqueue starts, but SET_VRING_CALL will be called when virtqueue is
>> initialized.
>> Not sure exactly, might be "vq->call" will be valid while connection is
>> established?
> Yes, it would be valid as far as we don't reset it from another
> set_vring_call. So, we should not reset it on reset_device().
>
> 	--yliu

Hi Yuanhan,

Thanks for checking.
I will submit the patch for this today.

Tetsuya

>> Also I've found a workaround.
>> Please execute after step7.
>>
>> 8. Bind the virtio-net device to virtio-pci kernel driver.
>> 9. Bind the virtio-net device to igb_uio.
>> 10. Start testpmd in QEMU.
>>
>> When step8 is executed, connection will be re-established, and testpmd
>> on host will be able to receive SET_VRING_CALL.
>> Then testpmd on host can start.
>>
>> Thanks,
>> Tetsuya