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[Xen-devel] [PATCH] Extensions to vmxassist to handle additional mode switch cases

  • To: <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "Kevin Tronkowski" <ktronkowski@xxxxxxxxxxxxxxx>
  • Date: Fri, 2 Jun 2006 09:27:15 -0400
  • Delivery-date: Fri, 02 Jun 2006 06:25:09 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcaGSDwMXs+hJ2u9T+WIhw7P0T6Q+Q==
  • Thread-topic: [PATCH] Extensions to vmxassist to handle additional mode switch cases

Oops, this is a resend with a subject line this time ;->

Attached is a patch which extends vmxassist to handle two cases 
related to mode switching found while experimenting with different 
boot loaders.

The first case is use of the JMP instruction with memory location 
operands to complete a switch to protected mode. This patch adds 
emulation for this form of the JMP instruction to vmxassist.

The second case is where boot loader code does not save/restore a 
non-zero SS register across a protected mode traversal. 
Zeroing the SS register in vmxassist results in all sorts of problems 
in the domU after returning back to real mode. This patch stores 
segment register values before entering protected mode and correctly 
restores the old values (instead of an incorrect zero value) when 
reentering real mode. 

Signed-off-by Kevin Tronkowski <ktronkowski@xxxxxxxxxxxxxxx>


Attachment: vm86.patch
Description: vm86.patch

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