Re: [Xen-devel] DMI and other BIOS hooks

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 26 Jul 2005, at 19:11, King, Steven R wrote:

> Here's a few specific questions:
> 1) Does Xen map the platform's 0xF0000-0xFFFFF BIOS space to guests, or
> is this region virtualized?
> 2) If virtualized, how Xen map BIOS facilities to guests?
>
> In my case, Dom0 finds the _DMI_ entry point, which appears to overlap
> with physical RAM.  This ultimately causes the domain_crash() for Dom0.
> Looks like a bad BIOS, but I'm unclear as to the degree which Xen plays
> man-in-the-middle.
Memory space that is reserved by the e820 table is marked as 'I/O 
memory' by Xen. Domain0 is allowed to map such areas as it wishes. If 
you have a broken BIOS that is not reserving the table areas in its 
e820, Xen will not mark the area as I/O memory and will prevent domain0 
from mapping that memory. Hence the crash.
We may need a workaround for broken BIOSes (perhaps even if it's just a 
boot parameter to Xen to specify reserved memory ranges).
 -- Keir


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