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Re: [Xen-devel] [patch] more correct pfn_valid()

On 19 May 2005, at 09:14, Tian, Kevin wrote:

For this part, I made a mistake to confuse domN and dom0. OK, for
paravirtualized guest, there's actually no I/O range for domN, since the
front driver in domN will do all things to communicate with backend in
Dom0. But what about a driver domain which has access to physical
device, thus need real I/O address?

We rely on the driver using the dma_coherent/pci_consistent/bus_address macros for mapping device memory. Originally designed to handle IOMMUs, it is handy for us to determine places where code is handling real machine physical addresses rather than pseudophysical addresses. This gets groans of distaste from the kernel maintainers but has worked enormously well so far (AGP needed patching separately though).

 -- Keir

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