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Re: [Xen-devel] [PATCH] Use virtual 8086 mode for VMX guests with CR0.PE == 0

  • To: "Tim Deegan" <Tim.Deegan@xxxxxxxxxx>
  • From: "Trolle Selander" <trolle.selander@xxxxxxxxx>
  • Date: Tue, 9 Dec 2008 20:58:02 -0500
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Tue, 09 Dec 2008 17:58:38 -0800
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Looks good. I tested it with OS/2 and Win 98, and there's no regressions in the realmode parts of their bootup, but quite a significant speedup of the boot process in both cases.


On Tue, Dec 9, 2008 at 11:18 AM, Tim Deegan <Tim.Deegan@xxxxxxxxxx> wrote:
When a VMX guest tries to enter real mode, put it in virtual 8086 mode
instead, if that's possible.  Handle all errors and corner cases by
falling back to the real-mode emulator.

This is similar to the old VMXASSIST system except it uses Xen's
x86_emulate emulator instead of having a partial emulator in the guest
firmware.  It more than doubles the speed of real-mode operation on VMX.

Signed-off-by: Tim Deegan <Tim.Deegan@xxxxxxxxxx>

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