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

["Kamble, Nitin A" <nitin.a.kamble@xxxxxxxxx>]

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.
>
> Regards,
>
> 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,
Nitin
Open Source Technology Center, Intel Corporation.
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