[Libvirt-cim] RFC : Introducing new CIM_RES_TYPE for 9pfs support on QEMU/KVM environment

[Sharad Mishra]

> Deepak Shetty <deepakcs at linux.vnet.ibm.com>
> Sent by: libvirt-cim-bounces at redhat.com
>
> 12/02/2011 05:13 AM
>
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> Re: [Libvirt-cim] RFC : Introducing new CIM_RES_TYPE for 9pfs
> support on QEMU/KVM environment
>
> On 12/02/2011 01:23 PM, Deepak Shetty wrote:
> > On 12/02/2011 04:32 AM, Sharad Mishra wrote:
> [...]
>  >> <filesystem type='mount'>
>  >> <driver type='handle'/>
>  >> <source dir='/tmp/virt1'/>
>  >> <target dir='test-lib'/>
>  >> <alias name='fs0'/>
>  >> <address type='pci' domain='0x0000' bus='0x00' slot='0x03'
>  >> function='0x0'/>
>  >> </filesystem>
>
> >> What in the above libvirt XML makes it specific to 9pfs?  I am
> >> looking for
> >> special 'tags'  or 'properties'.
> >>
> >> -Sharad Mishra
> > type='mount' makes it specific to 9pfs. So its the type attribute of
> > the filesystem tag.
> > I confirmed the same by looking into libvirt code also.
> >
> [...]
> >>> The<filesystem>  node comes directly under the<domain>  node.
> >>>
> >>> My approach for introducing 9pfs support in libvirt-cim is ...
> >>>
> >>> 1) Add a new CIM res type, eg; CIM_RES_TYPE_9PFS, is this ok ?
> >>>
> >>> 2) Add appropriate handlers for the above new resource type
> >>>
> >>> 3) Add new members in struct domain for representing this new device
> >> type.
> >>> 4) Add appropriate xml parsing generation tags for the new resource
> >>> type.
> >>>
> >>> 5) I probably need to add something like
> >>> KVM_9PFSResourceAllocationSettingData -- I am not very clear on this
> >>> yet.
> >>> Need some help on how to do this ?
> >>>
>
> I found some more enlightment today looking at the code, so here are my
> newer thoughts...
>
> 1) It looks like the <filesystem> libvirt xml node ( that comes directly
> under <devices>) is supported in a psuedo fashion, under
> CIM_RES_TYPE_DISK, is this correct ?
> It does res_type = ...DISK and dev_type = ..DISK_FS.

That is right. So, a filesystem is a disk device with type set to DISK_FS.

>
> 2) The cim code is structured in such a way that for each device type
> that comes under <devices> there is a virt-device and
> <device_type>_device (eg: disk_device, net_device) structures and they
> are described by the respective RASDs. In following this tradition the
> there should have been virt_device and fs_device structures to
> correspond to the <filesystem> device type, eventually getting embedded
> under 'struct domain' but I don't see it, why is this so ? Why is
> <filesystem> treated differently  in cim code ?

Not sure why its treated differently.

>
> 3) Assuming "yes" to #1 above, i need to extend the EmulatedType in
> KVM_DiskResourceAllocationSettingData to support "filesystem" as a
> value, set the disk_type = DISK_FS in disk_rasd_to_vdev and then it
> should probably work, as the disk_xml and disk_fs_xml code is already
> present to create the <filesystem> xml node.

Bulk of the code already exist. You may need to test it and fix some bugs.

>
> 4) I probably will re-use some of the members of
> KVM_DiskResourceAllocationSettingData from a 9pfs perspective, source
> and target will remain same as before, DriverCache, Address, may not be
> relevant for 9pfs. I might need to add few more stuff in DiskRASD as
> needed to support more sub-elements and attributes in for the
> <filesystem> in 9pfs case.

Depending on your requirement, you may have to add new properties.

-Sharad

>
> Let me know if the above approach/understanding is correct. Appreciate
> your inputs.
>
> thanx,
> deepak
>
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