On Mon, Nov 22, 2010 at 2:05 PM, Prasad Joshi
<[email protected]> wrote:
> I was under the impression that the each virtio driver will have a frontend 
> and backend part. The frontend part would be loaded in the Guest OS and the 
> backend driver will be loaded in the Host OS. These two drivers will 
> communicate with each other. The backend driver will then retransmit the 
> actual request to correct driver.
>
> But seems like my understanding is wrong.
> I attached a virtio disk to the Guest OS. When the Guest was booted, after 
> creating a file system on the attached disk I mounted it.
>
> [pra...@prasad-fedora12-vm ~]$ lsmod | grep -i virtio
> virtio_blk              7352  1
> virtio_pci              8680  0
> virtio_ring             6080  1 virtio_pci
> virtio                  5220  2 virtio_blk,virtio_pci
>
> But on the host machine no backend driver was loaded
>
> r...@prasad-desktop:~/VMDisks# lsmod | grep -i virtio
> r...@prasad-desktop:~/VMDisks#
>
> Does this mean there is no explicit backend driver?

A virtio device is a PCI adapter in the guest.  That's why you see virtio_pci.

The userspace QEMU process (called qemu-kvm or qemu) does device
emulation and contains the virtio code you are looking for.  See
hw/virtio-blk.c in qemu-kvm.git.

Stefan
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