> frnds, i am confuse regarding the role of tap interface and its handling
> within Xen from developer perspective. Can anyboyd useful insights or
> usefuill links about it.
I''m not sure which interface you mean, so I''ll cover both
possibilities:
There''s the Linux tun / tap network interface. This allows a userspace
process to create a virtual network device. This is used by the Qemu-based
device model in order to supply emulated network services for HVM virtual
machines.
There''s also the blktap interface. This is used to provide some forms
of
virtual disk storage for domains: currently supported are file-based storage
and the QCow copy-on-write format. This should work for HVM or paravirt
domains (although I''ve heard conflicting reports about how well it
works for
HVM at the moment). Blktap is implemented by allowing a userspace process to
satisfy the virtual IO requests from the guests; the userspace blocktap
process is then able to issue the appropriate IOs on the guest''s
behalf.
There''s also a device mapper plugin called dm-userspace that offers
some
similar functionality to blktap. I''m not sure what the status of this
is
right now, though.
Hope that helps you some,
Cheers,
Mark
--
Dave: Just a question. What use is a unicyle with no seat? And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!
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