Arnd Bergmann wrote:
One interesting aspect of the PS3 hypervisor is that some of the
low-speed interfaces are implemented as a virtual UART, meaning
something that only has read and write operations and uses an
interrupt for flow control. The implementation in
drivers/ps3/vuart.c is probably more complex than what we want
as a generic transport mechanism, but simply having a bidirectional
data stream sounds like an ideal abstraction for the "simple"
case. Some more or less obvious users of this include:
- console
- additional tty
- random
- slow network (using ppp)
- printer
- watchdog
- hid (e.g. mouse)
- system management (like ps3)
- fast network (in combination with
shared memory segment)
The transport can be hypervisor specific, e.g. there could be
a virtual PCI serial port on kvm, an hcall interface on the ps3
and a virtual CTC on s390 (kidding), while all of them can have
the same kind of hardware _behind_ the serial connection.
Note that at least for PIO-based devices, there is nothing that says you
can't implement PCI over another transport, if you wish. It's really
just a very simple RPC protocol.
DMA is trickier, as it makes the data appear into the address space of
the guest in a way that is both device- and host-dependent (in the
presence of PCI domains, IOMMU etc.) There may be reason to avoid DMA
for that reason.
-hpa
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
