[dpdk-dev] rte_eth_dev_attach returns 0, although device is not attached

[Igor Ryzhov]

> 4 авг. 2016 г., в 16:21, Ferruh Yigit <ferruh.yigit at intel.com> написал(а):
> 
> On 8/4/2016 12:51 PM, Igor Ryzhov wrote:
>> Hello Ferruh,
>> 
>>> 4 авг. 2016 г., в 14:33, Ferruh Yigit <ferruh.yigit at intel.com> написал(а):
>>> 
>>> Hi Igor,
>>> 
>>> On 8/3/2016 5:58 PM, Igor Ryzhov wrote:
>>>> Hello.
>>>> 
>>>> Function rte_eth_dev_attach can return false positive result.
>>>> It happens because rte_eal_pci_probe_one returns zero if no driver is found for the device:
>>>> ret = pci_probe_all_drivers(dev);
>>>> if (ret < 0)
>>>> 	goto err_return;
>>>> return 0;
>>>> (pci_probe_all_drivers returns 1 in that case)
>>>> 
>>>> For example, it can be easily reproduced by trying to attach virtio device, managed by kernel driver.
>>> 
>>> You are right, and I did able to reproduce this issue with virtio as you
>>> suggest.
>>> 
>>> But I wonder why rte_eth_dev_get_port_by_addr() is not catching this.
>>> Perhaps a dev->attached check needs to be added into this function.
> 
> With a second check, rte_eth_dev_get_port_by_addr() catches it if the
> driver is missing.
> 
> But for virtio case, problem is not missing driver.
> Problem is eth_virtio_dev_init() is returning a positive value on fail.
> 
> Call stack is:
> rte_eal_pci_probe_one
>    pci_probe_all_drivers
>        rte_eal_pci_probe_one_driver
>            rte_eth_dev_init
>               eth_virtio_dev_init
> 
> So rte_eal_pci_probe_one_driver() also returns positive value, as no
> driver found, and rte_eth_dev_get_port_by_addr() returns a valid
> port_id, since rte_eth_dev_init() allocated an eth_dev.
> 
> Briefly, this can be fixed in virtio pmd, instead of eal pci.
> 
>>> 
>>>> 
>>>> I think it should be:
>>>> ret = pci_probe_all_drivers(dev);
>>>> if (ret)
>>>> 	goto err_return;
>>>> return 0;
>>> 
>>> Your proposal looks good to me. Will you send a patch?
>> 
> 
> Original code silently ignores the if driver is missing for that dev,
> although it is still questionable, I think we can keep this as it is.
> 
>> Patch sent.
> 
> Sorry for this, but can you please test with following modification in
> virtio:
> index 07d6449..c74eeee 100644
> --- a/drivers/net/virtio/virtio_ethdev.c
> +++ b/drivers/net/virtio/virtio_ethdev.c
> @@ -1156,7 +1156,7 @@ eth_virtio_dev_init(struct rte_eth_dev *eth_dev)
>        if (pci_dev) {
>                ret = vtpci_init(pci_dev, hw, &dev_flags);
>                if (ret)
> -                       return ret;
> +                       return -1;
>        }
> 
>        /* Reset the device although not necessary at startup */

I think it's not a good change, because it will break the idea of this patch - http://dpdk.org/browse/dpdk/commit/?id=ac5e1d83 <http://dpdk.org/browse/dpdk/commit/?id=ac5e1d83>

Also, with your patch the application will not start, because rte_eal_pci_probe will fail:

	if (ret < 0)
		rte_exit(EXIT_FAILURE, "Requested device " PCI_PRI_FMT
			 " cannot be used\n", dev->addr.domain, dev->addr.bus,
			 dev->addr.devid, dev->addr.function);

And now I think that maybe we should change the way rte_eal_pci_probe works.
I think we shouldn't stop the application if just one of PCI devices is not probed successfully.

> 
> 
>> 
>>> 
>>>> Best regards,
>>>> Igor