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Date: Tue, 22 Dec 2015 17:56:41 +0800
From: Peter Xu <peterx@redhat.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>
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Cc: DPDK Dev <dev@dpdk.org>
Subject: Re: [dpdk-dev] [Question] How pmd virtio works without UIO?
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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.

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.

Thanks
Peter

> 
> 	--yliu