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

[Xie, Huawei]

On 12/22/2015 6:48 PM, 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.
>
>> 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.
>> Thanks
>> Peter
>>
>>> 	--yliu
>