Re: bus_space/bus_dma and PAE

[Christoph Egger <Christoph_Egger%gmx.de@localhost>]

Manuel Bouyer wrote:
> On Sun, Jan 25, 2009 at 11:30:43AM +0100, Christoph Egger wrote:
>> Manuel Bouyer wrote:
>>> Hi,
>>> I started looking at PCI passthough for Xen, and as part of this
>>> at getting a XEN3PAE i386 kernel building (which is usefull if we ever want
>>> to suppport native i386 PAE too). The attached patch allows to build
>>> a XEN3PAE_XENU kernel with bus_space and bus_dma linked in.
>>> What it does is change bus_addr_t to be paddr_t (so its size changes with
>>> options PAE); and remplace a view bus_addr_t with vaddr_t where
>>> the value is used as a virtual address (and so is not a physical bus
>>> address, strictly speaking).
>>>
>>> comment ?
>> Does that finally allow us to use the BIOS memory map code in
>> x86/x86/x86_machdep.c generally in Xen ?
> 
> Of what use would this be ? DomU don't have access to the BIOS map AFAIK,
> and I can't see what this would buy us to fake one.

You get the BIOS map via

err = HYPERVISOR_memory_op(XENMEM_memory_map, &memmap);

and it is useful to deal with PCI memory holes which you have in
a Dom0 anyway and also in a DomU with PCI passthrough.

Christoph