[dpdk-dev] [PATCH v4 0/2] Add VHOST PMD

[Yuanhan Liu]

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
> 
> 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