Sorry for the late reply, and thanks Jano for pointing out elsewhere
that this didn't receive a response.
On 8/12/19 5:56 AM, Li Feng wrote:
Hi Guys,
And I want to add the vhost-user-scsi-pci/vhost-user-blk-pci support
for libvirt.
The usage in qemu like this:
Vhost-SCSI
-chardev socket,id=char0,path=/var/tmp/vhost.0
-device vhost-user-scsi-pci,id=scsi0,chardev=char0
Vhost-BLK
-chardev socket,id=char1,path=/var/tmp/vhost.1
-device vhost-user-blk-pci,id=blk0,chardev=char1
Indeed that matches what I see for the qemu commits too:
https://git.qemu.org/?p=qemu.git;a=commit;h=00343e4b54b
https://git.qemu.org/?p=qemu.git;a=commit;h=f12c1ebddf7
What type should I add for libvirt.
Type1:
<hostdev mode='subsystem' type='vhost-user'>
<source protocol='vhost-user-scsi' path='/tmp/vhost-scsi.sock'></source>
<alias name="vhost-user-scsi-disk1"/>
</hostdev>
Type2:
<disk type='network' device='disk'>
<driver name='qemu' type='raw' cache='none' io='native'/>
<source protocol='vhost-user' path='/tmp/vhost-scsi.sock'>
</source>
<target dev='sdb' bus='vhost-user-scsi'/>
<boot order='3'/>
<alias name='scsi0-0-0-1'/>
<address type='drive' controller='0' bus='0' target='0' unit='1'/>
</disk>
<disk type='network' device='disk'>
<driver name='qemu' type='raw' cache='none' io='native'/>
<source protocol='vhost-user' path='/tmp/vhost-blk.sock'>
</source>
<target dev='vda' bus='vhost-user-blk'/>
<boot order='1'/>
<alias name='virtio-disk0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x07'
function='0x0'/>
</disk>
I think wiring this into <disk> makes more sense. <hostdev> is really an
abstraction for assigning a (typically) physical host device to the VM,
so it handles things like hiding a PCI device from the host, and passing
that exact device to the VM.
In the vhost-user-scsi/blk case, the host device is just a special
process running on the other side of a socket, and the device
represented to the guest is a typical virtio device. So to me it makes
more sense as a <disk> with a <source> that points at that socket.
target bus=virtio vs bus=scsi is already used to distinguish between
virtio-blk and virtio-scsi, so I think we can keep that bit as is, with
the <address type=drive|pci> to match. We just need to differentiate
between plain virtio and vhost-user
network devices already have vhostuser support:
<interface type='vhostuser'>
<source type='unix' path='/tmp/vhost1.sock' mode='server|client'/>
<model type='virtio'/>
</interface>
Internally that <source> is a virDomainChrSourceDefPtr which is our
internal representation of a chardev. So I think something akin to this
is the way to go. It will likely require updating a LOT of places in the
code that check disk type= field, probably most places that care about
whether type=NETWORK or type=!NETWORK will need to be mirrored for the
new type.
<disk type='vhostuser' device='disk'>
<source type='unix' path='/path/to/vhost-user-blk.sock' mode='client'/>
<target dev='vda' bus='virtio'/>
</disk>
<disk type='vhostuser' device='disk'>
<source type='unix' path='/path/to/vhost-user-scsi.sock' mode='client'/>
<target dev='sda' bus='scsi'/>
</disk>
- Cole
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