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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: Fri, 30 Mar 2007 14:08:33 -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,

On Fri, 2007-03-30 at 14:00 -0500, Anthony Liguori wrote:
    /* Enter real mode, reload all segment registers and IDT. */
    "    ljmp $0x8,$0x0              \n"
    "trampoline_start: .code16       \n"
    "    mov  %eax,%cr0              \n"

That change was pretty recent so unless it was reverted it should Just Work.


Anthony Liguori
Now I see cr0 is updated after returning from main.
   I enabled the debug log in the xen code now.

(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) vmx_vmexit_handler called. eip = 0x0                                     
(XEN) vmx_cr_access called eip=0x0                                             
(XEN) mov_to_cr 0 called eip=0x0                                               
(XEN) vmx_set_cr0 called eip=0x0                                               
(XEN) Transfering -- control to x86_emulate eip 0x0                            
(XEN) hvm.c:446:d2 Triple fault on VCPU0 - invoking HVM system reset. 

It shows cr0 is getting modified. But the eip is still 0x0.

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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