RE: [Xen-devel] Calling __va() in a x86_64 Dom0 module

["Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>]

> I am trying to get a module working under x86_64 Dom0. The 
> module is used to communicate between the Linux OS running on 
> the ES7000 and the external service processor. The module as 
> part of its setup parses the OEM table to reference some 
> information present there. It gets the address of the OEM 
> table using acpi_get_firmware_table(). Then the address is 
> converted to a virtual address using __va() before it is referenced.
> 
> When building the module against 2.6.12-dom0, the __va() 
> function that is called the x86_64 one. When I try accessing 
> the VA of the OEM table, I am getting a page fault. The PA is 
> 0x26e0400.  So I patched the module to use Xen's __va() 
> function. Now the page fault does not happen but when the 
> table is parsed the information I am looking for is not present. 
> 
> Am I doing anything wrong here? Am I not supposed to touch 
> this region of memory from Dom0? Or is there a hypercall that 
> I should be using?

dom0 only has the bottom 1MB of machine memory mapped, so if you want to
access outside of this you'll need to map it yourself using
direct_remap_pfn_range. 

Ian
 

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