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[Xen-devel] Re: [PATCH][RFC] Emulating real mode with x86_emulate

To: "Anthony Liguori" <aliguori@xxxxxxxxxx>
Subject: [Xen-devel] Re: [PATCH][RFC] Emulating real mode with x86_emulate
From: "Kamble, Nitin A" <nitin.a.kamble@xxxxxxxxx>
Date: Thu, 29 Mar 2007 19:20:14 -0700
Cc: "Yu, Wilfred" <wilfred.yu@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Keir Fraser <keir@xxxxxxxxxxxxx>, "Nakajima, Jun" <jun.nakajima@xxxxxxxxx>
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Thread-topic: [PATCH][RFC] Emulating real mode with x86_emulate
Hi Anthony,
  With the new revision I am able to get the -emulate-16bit command line switch working.

(XEN) HVM2: Creating MP tables ...                                             
(XEN) HVM2: Loading Cirrus VGABIOS ...                                         
(XEN) HVM2: Loading ACPI ...                                                   
(XEN) HVM2: Loading VMXAssist ... deadbeef                                     
(XEN) HVM2: foo                                                                
(XEN) hvmop_emulate_realmode                                                   
(XEN) guest requests real mode emulation                                       
(XEN) foo 221                                                                  
(XEN) HVM2: Invoking ROMBIOS ...                                               
(XEN) hvm.c:446:d2 Triple fault on VCPU0 - invoking HVM system reset.

I have not added any debug lines in the code yet, and I don't know how far is the emulator going. I will check it tomorrow.

Thanks & Regards,
Open Source Technology Center, Intel Corporation.
The mind is like a parachute; it works much better when it's open.

On Thu, 2007-03-29 at 17:59 -0700, Nitin A Kamble wrote:
On Thu, 2007-03-29 at 19:11 -0500, Anthony Liguori wrote:

Okay, you'll need to make sure that hvmloader and qemu are both being 
rebuilt and reinstalled.

I am sure both are built with the patch and installed correctly.

The really curious thing is that eip from the VMCS is set to 0.  eip 
should be address of the EIP of whatever movl cr0 instruction that 
occurs when returning from main() in hvmloader.

I also find that x86_emulate() is never called while emulate_realmode is set in the hypervisor.

I guess it's possible that if you are using a version of unstable that 
predates Keir's recent hvmloader changes, you wouldn't have hvmloader 
switching to real mode.  That could explain some of the weirdness you're 
seeing.  What changeset are you on?
So far I am using: r14560_20070326

Now I am trying with: r14631_20070329

Thanks & Regards,
Open Source Technology Center, Intel Corporation.
The mind is like a parachute; it works much better when it's open.

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