dev/virtio stuff

Bryan Venteicher bryanv at
Tue Oct 30 05:52:30 UTC 2012


----- Original Message -----
> From: "Sean Bruno" <seanbru at>
> To: freebsd-virtualization at
> Sent: Monday, October 29, 2012 4:49:42 PM
> Subject: dev/virtio stuff
> So ... I see we have virtio nowish.  I've started my hackery to make
> some man(4) pages for this, but have some questions.  Doing some raw
> QEMU things, I can't quite see how to get the virtio blk and net
> devices working.

There are already virtio(4) man pages, but it looks like they didn't
get MFC to 9.

> I've loaded the virtio drivers as modules.  Is this not going to work in
> this case?  I don't see the virtio versions of disk devices in /dev
> so I'm not sure what the problem here is.

>> FreeBSD 7.5-YAHOO-20121028 #0 ybsd_9 at 324991: Sun Oct 28 22:08:46 UTC 2012
>>    kernel at amd64

I assume this is 9-STABLE'ish?

>> virtio_pci0: <VirtIO PCI Block adapter> port 0xc200-0xc23f irq 11 at device 4.0 on pci0
>> vtblk0: <VirtIO Block Adapter> on virtio_pci0
>> virtio_pci0: host features: 0x41000014 <NotifyOnEmpty,DiskGeometry,MaxNumSegs>
>> virtio_pci0: negotiated features: 0x14 <DiskGeometry,MaxNumSegs>
>> vtblk0: 4096MB (8388608 512 byte sectors)

The VirtIO block gets probed and attached correctly, and right after the
last printf, hands off to disk_create(9) to create the GEOM plumbing and
device. VirtIO block devices get created as vtbdX, not as ad, ada, or da.

Can you see if g_disk_create() gets called (with flag==EV_CANCEL)?
What does a verbose boot show?


> Sean
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