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Re: [Xen-devel] Consuming PCI device in PV kernel

On Mon, 2014-07-21 at 11:13 +0100, Simon Martin wrote:
> Hello Konrad,
> Friday, July 18, 2014, 8:09:42 PM, you wrote:
> >> I  now  have  a  working implementation of my own pcifront based on the
> >> mini-os  implementation,  however I can't seem to find any examples or
> >> documentation  anywhere on how to discover and map the PCI device into
> >> my PV memory map.
> > Not sure what 'PV memory map' means? You mean the BAR values and such?
> That's exactly what I mean. I assume that BAR entries must be written
> pointing to an absolute memory area in dom0 which will then be mapped
> into the PV as this provides the greatest flexibility. Is this
> correct? Or do I just enable a memory area in the PV and map the BAR
> to the buffers physical address?

IIRC from the guest PoV you just need to read the BAR values from the
CFG space and then use them without worrying about where they point,
i.e. by creating virtual address mappings of whatever MMIO address the
BAR gives you.

The initial setup of the BAR registers is handled either by the BIOS or
the dom0 kernel if it feels the need to do reassignment, you shouldn't
need to worry about it I don't think.


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