[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Realtime access to PCI NIC
On Mon, 2014-07-07 at 13:21 +0100, Simon Martin wrote: > Hi all, > > I am reading through the mini-os pcifront.c as an example of how to > implement direct access to a PCI device. However looking at the code > all access seems to go via the PCI Backend driver, which means that I > am subject to the latencies and jitter of the Xen scheduling. Only PCI cfg reads/writes go via the backend, I think. Any MMIO space (i.e. described in the PCI BARS) can be directly mapped, likewise for the IO port spaces associated with the device. I think PCI cfg space is only generally used during probing/setup etc. Hopefully you don't need to poke it at runtime? > Reading the documentation about PCI Passthrough I imagined that I > would have direct access to the PCI hardware once the handover from > dom0 as performed. Is that correct? If so, how do I implement that? > > I am using an Intel processor that has VT-d so that should be > possible. Right, VT-d allows the MMIO stuff to be mapped to an HVM guest (PV doesn't even need that), but unfortunately there are bits in the pci cfg space which even a guest with the device passed to it shouldn't be able to mess with (I don't know the details though). Ian. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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