Re: [dpdk-dev] [Question] How pmd virtio works without UIO?

["Xie, Huawei" <huawei.xie@intel.com>]

On 12/22/2015 7:39 PM, Peter Xu wrote:
> On Tue, Dec 22, 2015 at 10:47:21AM +0000, Xie, Huawei wrote:
>> On 12/22/2015 5:57 PM, Peter Xu wrote:
>>> On Tue, Dec 22, 2015 at 04:32:46PM +0800, Yuanhan Liu wrote:
>>>> Actually, you are right. I mentioned in the last email that this is
>>>> for configuration part. To answer your question in this email, you
>>>> will not be able to go that further (say initiating virtio pmd) if
>>>> you don't unbind the origin virtio-net driver, and bind it to igb_uio
>>>> (or something similar).
>>>>
>>>> The start point is from rte_eal_pci_scan, where the sub-function
>>>> pci_san_one just initates a DPDK bond driver.
>>> I am not sure whether I do understand your meaning correctly
>>> (regarding "you willl not be able to go that furture"): The problem
>>> is that, we _can_ run testpmd without unbinding the ports and bind
>>> to UIO or something. What we need to do is boot the guest, reserve
>>> huge pages, and run testpmd (keeping its kernel driver as
>>> "virtio-pci"). In pci_scan_one():
>>>
>>> 	if (!ret) {
>>> 		if (!strcmp(driver, "vfio-pci"))
>>> 			dev->kdrv = RTE_KDRV_VFIO;
>>> 		else if (!strcmp(driver, "igb_uio"))
>>> 			dev->kdrv = RTE_KDRV_IGB_UIO;
>>> 		else if (!strcmp(driver, "uio_pci_generic"))
>>> 			dev->kdrv = RTE_KDRV_UIO_GENERIC;
>>> 		else
>>> 			dev->kdrv = RTE_KDRV_UNKNOWN;
>>> 	} else
>>> 		dev->kdrv = RTE_KDRV_UNKNOWN;
>>>
>>> I think it should be going to RTE_KDRV_UNKNOWN
>>> (driver=="virtio-pci") here. I tried to run IO and it could work,
>>> but I am not sure whether it is safe, and how.
>> Good catch, peter.
>> Actually recently customers complain that with this feature, DPDK always
>> tries to take over this virtio-pci device, which is unwanted behavior.
>> Using blacklist could workaround this issue.
>> However, the real serious problem is that kernel driver is still
>> managing this device.
>>
>> Changchun, Thomas:
>> I think we should fix this, but firstly i wonder why using port IO to
>> get PCI resource is more secure.
> I am not familiar with this, however, shouldn't port IO from
> userspace the most dangerous way to access PCI resource?
>
>>> Also, I am not sure whether I need to (at least) unbind the
>>> virtio-pci driver, so that there should have no kernel driver
>>> running for the virtio device before DPDK using it.
>> If you unbind, you have no entry under /proc/ioports for virtio IO port.
> I tried to unbind one of the virtio net device, I see the PCI entry
> still there.
>
> Before unbind:
>
> [root@vm proc]# lspci -k -s 00:03.0
> 00:03.0 Ethernet controller: Red Hat, Inc Virtio network device
>         Subsystem: Red Hat, Inc Device 0001
>         Kernel driver in use: virtio-pci
> [root@vm proc]# cat /proc/ioports | grep c060-c07f
>   c060-c07f : 0000:00:03.0
>     c060-c07f : virtio-pci
>
> After unbind:
>
> [root@vm proc]# lspci -k -s 00:03.0
> 00:03.0 Ethernet controller: Red Hat, Inc Virtio network device
>         Subsystem: Red Hat, Inc Device 0001
> [root@vm proc]# cat /proc/ioports | grep c060-c07f
>   c060-c07f : 0000:00:03.0
>
> So... does this means that it is an alternative to black list
> solution?
Users wants to use virtio-net device for normal communication, so they
still want virtio-net driver to manipulate this device. They don't want
DPDK to take over this device blindly.
>
> Peter
>
>>> Thanks
>>> Peter
>>>
>>>> 	--yliu