Messages in this thread | | | Date | Tue, 14 Apr 2009 15:27:16 -0700 | From | David Hawkins <> | Subject | Re: [RFC v2] virtio: add virtio-over-PCI driver |
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Hi Grant,
> Hmmm, I hadn't thought about this. I was intending to use the > Virtex's memory region for all virtio, but if I can allocate memory > regions on both sides of the PCI bus, then that may be best.
Sounds like you can experiment and see what works best :)
>> If you use >> a PCI Target only core, then the MPC5200 DMA controller >> will have to do all the work, and read transfers might >> be slightly less efficient. > > I'll definitely intend to enable master mode on the Xilinx PCI controller.
Since you understand the lingo, you clearly understand there are core differences :)
>> Our target boards (PowerPC) live in compactPCI backplanes >> and talk to x86 boards that do not have DMA controllers. >> So the PCI target board DMA controllers are used to >> transfer data efficiently to the x86 host (writes) >> and less efficiently from the host to the boards >> (reads). Our bandwidth requirements are 'to the host', >> so we can live with the asymmetry in performance. > > Fortunately I don't have very high bandwidth requirements for the > first spin, so I have some room to experiment. :-)
Yes, in theory you have enough bandwidth ... then a few features are added, the PCI core is not quite as fast as advertised, etc etc :)
Cheers, Dave
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