Re: rte_eth_dev_attach returns 0, although device is not attached

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

On 8/4/2016 12:51 PM, Igor Ryzhov wrote:
> Hello Ferruh,
> 
>> 4 авг. 2016 г., в 14:33, Ferruh Yigit <ferruh.yigit@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 */


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