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

[Peter Xu]

On Wed, Dec 23, 2015 at 10:01:35AM +0800, Yuanhan Liu wrote:
> On Tue, Dec 22, 2015 at 05:56:41PM +0800, 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.
> 
> Sorry, I simply overlook that. I was thinking it will quit here for
> the RTE_KDRV_UNKNOWN case.
> 
> > I tried to run IO and it could work,
> > but I am not sure whether it is safe, and how.
> 
> I also did a quick test then, however, with the virtio 1.0 patchset
> I sent before, which sets the RTE_PCI_DRV_NEED_MAPPING, resulting to
> pci_map_device() failure and virtio pmd is not initiated at all.

Then, will the patch work with ioport way to access virtio devices?

> 
> > 
> > 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.
> 
> Why not? That's what the DPDK document asked to do
> (http://dpdk.org/doc/guides/linux_gsg/build_dpdk.html):
> 
>     3.6. Binding and Unbinding Network Ports to/from the Kernel Modules
>     
>     As of release 1.4, DPDK applications no longer automatically unbind
>     all supported network ports from the kernel driver in use. Instead,
>     all ports that are to be used by an DPDK application must be bound
>     to the uio_pci_generic, igb_uio or vfio-pci module before the
>     application is run. Any network ports under Linux* control will be
>     ignored by the DPDK poll-mode drivers and cannot be used by the
>     application.

This seems obsolete? since it's not covering ioport.

Peter

> 
> 
> 	--yliu