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

[Xie, Huawei]

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