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Re: [Xen-devel] Re: xen-kernel and EDD

  • To: Lin-Bao Zhang <2004.zhang@xxxxxxxxx>
  • From: Keir Fraser <keir.xen@xxxxxxxxx>
  • Date: Wed, 31 Aug 2011 08:56:58 +0100
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Wed, 31 Aug 2011 00:58:43 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: Acxns47UjyV7nQWvrUGa7iMi9ul4tw==
  • Thread-topic: [Xen-devel] Re: xen-kernel and EDD

On 31/08/2011 08:50, "Lin-Bao Zhang" <2004.zhang@xxxxxxxxx> wrote:

> about this topic , it doesn't end.
> in fact, we can't arbitrarily hard-code any number ,including
> BOOT_TRAMPOLINE and stack(%esp).
> I will special begin a new thread to discuss this question whose
> subject is "define BOOT_TRAMPOLINE and stack based on result of
> probing EBDA area by INT12"

Since the maximum EBDA size is 128kB, we should be fine sitting entirely
below 0x80000? Anyway, you otherwise have a chicken-and-egg situation: we
set up the trampoline to be able to execute real-mode code, and we need to
be in real mode to make legacy BIOS calls, hence we'd need to have the
trampoline set up to be able to make the BIOS call to decide where to locate
the trampoline. Which is a circular dependency.

 -- Keir

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