Re: [Xen-devel] [PATCH] xen: find a better location for the real-mode trampoline

[Paolo Bonzini <pbonzini@xxxxxxxxxx>]

Il 18/12/2012 14:36, Jan Beulich ha scritto:
>>>> >>> No, just busy.  I agree that checking all three is best.  However, 
>>>> >>> there
>>>> >>> is at least one known case where 0x40e doesn't work, so 0x413 and
>>>> >>> multiboot should be enough.
>>> >> 
>>> >> Can you provide more detail about this specific case? In
>>> >> particular, what value 0x40e in fact has there?
>> > 
>> > Sure.  0x40e did point to the beginning of the EBDA (around 635k), but
>> > an option ROM was reserving memory below there by lowering 0x413.
>> > That's the "on some machines" in the commit message.
> That wouldn't preclude the suggested sanity-checked-minimum
> solution.

Yes, on the other hand [0x413] should always be less than or equal to
[0x40e] << 6.  Otherwise for example DOS would not work on that system.

Paolo

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