Re: [Xen-devel] Virtualization project idea

[Dhananjay Goel <dhananjaygoel123@xxxxxxxxx>]

Also you wouldn't see the changes made in other VMs,
unless you made sure all the caches are refreshed etc in the VM all the time.

You'd need to use some cluster-filesystem (GFS, GFS2, OCFS2, GPFS, etc).

--Can you please suggest how NFS manages this because this case is handled by NFS without any corruption?

We can share flash drive across VMs as we do with physical machines in LAN. Please help!

Thanks,
Dhananjay

On Fri, Aug 27, 2010 at 4:27 PM, Pasi Kärkkäinen <pasik@xxxxxx> wrote:

On Fri, Aug 27, 2010 at 02:53:54PM +0530, Dhananjay Goel wrote:
>    This won't be straight forward. Think about USB memory/flash stick.
>    If every VM sees it, and simultaneously writes to it, the filesystem
>    in it will get corrupted immediately!
>
>    --Why would it get corrupted immediately. Might be we can just lock a
>    specific file which is being edited? Please suggest.
>

Because USB level has no idea about filesystems or files, or locking them!

Say you're using ext3 or NTFS in the VM for the USB device.
Those filesystems are NOT cluster-aware, ie. they're not aware of any sharing,
and they don't support any kind of sharing.

They expect exclusive access to the device.

If suddenly the bits on the device change from outside,
the filesystem gets corrupted very easily.

Also you wouldn't see the changes made in other VMs,
unless you made sure all the caches are refreshed etc in the VM all the time.

You'd need to use some cluster-filesystem (GFS, GFS2, OCFS2, GPFS, etc).

-- Pasi

>    Thanks,
>    Dhananjay

>
>    On Fri, Aug 27, 2010 at 2:49 PM, Pasi Kärkkäinen <[1]pasik@xxxxxx> wrote:
>
>      On Fri, Aug 27, 2010 at 02:45:12PM +0530, Dhananjay Goel wrote:
>      >    No, that's not possible with pvusb. pvusb is for direct passthru to
>      >    one/single vm.
>      >    You'd need some filesystem share (cifs/nfs/whatnot) to make such
>      sharing
>      >    possible.
>      >    Comments: Is it possible to share USB keyboard, USB mouse, USB
>      modem, etc
>      >    across VMs i.e host and guest(s)? If we connect USB keyboard, is it
>      >    possible to use it in guests?
>      >
>
>      This is implemented in XCI (Xen Client Initiative), and there has been
>      some discussions how to get it traditional Xen, to help Xen VGA
>      Passthrough usage.
>

>      See: [2]http://wiki.xensource.com/xenwiki/XenVGAPassthrough

>      >    Also, is it possible for us to modify the device driver of USB 2.0
>      so that
>      >    all USB 2.0 devices are visible and can be used across all VMs?
>      Please
>      >    suggest.
>      >
>
>      This won't be straight forward. Think about USB memory/flash stick.
>      If every VM sees it, and simultaneously writes to it, the filesystem
>      in it will get corrupted immediately!
>
>      USB Passthru cannot be used to 'share' devices, it's for giving
>      one/single VM
>      direct access to the device.
>
>      -- Pasi
>
>      >    Thanks,
>      >    Dhananjay
>      >
>      >    On Fri, Aug 27, 2010 at 2:16 PM, Pasi Kärkkäinen

>      <[1][3]pasik@xxxxxx> wrote:
>      >
>      >      On Fri, Aug 27, 2010 at 01:37:49PM +0530, Dhananjay Goel wrote:
>      >      >    Hi James/Pasi,
>      >      >    I had a look at

>      >      [1][2][4]http://wiki.xensource.com/xenwiki/XenUSBPassthrough

>      >      >    But I'm not sure if it supports sharing USB devices across
>      VMs
>      >      (host and
>      >      >    guest) i.e. if I plug in a flash drive then it would detect
>      in both
>      >      host
>      >      >    and guest and I'd be able edit files from all VMs rather
>      than
>      >      mounting and
>      >      >    unmounting everytime from 1 VM to other.
>      >      >    Please let me know your thoughts on it.
>      >      >
>      >
>      >      No, that's not possible with pvusb. pvusb is for direct passthru
>      to
>      >      one/single vm.
>      >      You'd need some filesystem share (cifs/nfs/whatnot) to make such
>      sharing
>      >      possible.
>      >
>      >      -- Pasi
>      >      >    Thanks,
>      >      >    Dhananjay
>      >      >
>      >      >    On Fri, Aug 27, 2010 at 4:28 AM, James Harper

>      >      >    <[2][3][5]james.harper@xxxxxxxxxxxxxxxx> wrote:
>      >      >
>      >      >      > Hi there!
>      >      >      >
>      >      >      > First I'd like to say that XEN plaform is really cool
>      and
>      >      awesome.
>      >      >      >
>      >      >      > I'm an engineering student and is searching for a
>      feasible
>      >      project in
>      >      >      > virtualization. I'd like to know if its possible to
>      share USB
>      >      devices
>      >      >      (flash
>      >      >      > drive, hard disk, mouse, keyboards etc) across guests
>      and host
>      >      (VMs).
>      >      >      Also, do
>      >      >      > you have any idea to extend it? Or any innovative idea
>      so that
>      >      we can
>      >      >      > implement it.
>      >      >      >
>      >      >      > I'd appreciate any help. Thanks in advance.
>      >      >      >
>      >      >
>      >      >      Further to what Pasi said, I have partially ported the
>      backend
>      >      interface
>      >      >      and can hand you the code if you want. It's probable a bit
>      stale
>      >      vs the
>      >      >      current kernels and leaks memory under some circumstances
>      but is
>      >      >      probably better than starting from scratch.
>      >      >      James
>      >      >
>      >      > References
>      >      >
>      >      >    Visible links

>      >      >    1. [4][6]http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>      >      >    2. mailto:[5][7]james.harper@xxxxxxxxxxxxxxxx
>      >
>      > References
>      >
>      >    Visible links

>      >    1. mailto:[8]pasik@xxxxxx

>      >    2. [9]http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>      >    3. mailto:[10]james.harper@xxxxxxxxxxxxxxxx
>      >    4. [11]http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>      >    5. mailto:[12]james.harper@xxxxxxxxxxxxxxxx

>
> References
>
>    Visible links
>    1. mailto:pasik@xxxxxx

>    2. http://wiki.xensource.com/xenwiki/XenVGAPassthrough
>    3. mailto:pasik@xxxxxx

>    4. http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>    5. mailto:james.harper@xxxxxxxxxxxxxxxx
>    6. http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>    7. mailto:james.harper@xxxxxxxxxxxxxxxx

>    8. mailto:pasik@xxxxxx

>    9. http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>   10. mailto:james.harper@xxxxxxxxxxxxxxxx
>   11. http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>   12. mailto:james.harper@xxxxxxxxxxxxxxxx

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