Re: [kvm-devel] Protected mode transitions and big real mode... still an issue

[Anthony L. <an...@co...>]

Guillaume Thouvenin wrote:
> Hello,
>
>  This patch should solve the problem observed during protected mode
> transitions that appears for example during the installation of
> openSuse-10.3. Unfortunately there is an issue that crashes
> kvm-userspace. I'm not sure if it's a problem introduced by the
> patch or if the patch is good and raises a new issue.
>   

You still aren't emulating the instructions correctly I think.  Running 
your patch, I see:

[  979.755349] Failed vm entry (exit reason 0x21) invalid guest state
[  979.755354] emulation at (46e4b) rip 6e0b: ea 10 6e 18
[  979.755358] successfully emulated instruction
[  979.756105] Failed vm entry (exit reason 0x21) invalid guest state
[  979.756109] emulation at (46e50) rip 6e10: 66 b8 20 00
[  979.756111] successfully emulated instruction
[  979.756749] Failed vm entry (exit reason 0x21) invalid guest state
[  979.756752] emulation at (46e54) rip 6e14: 8e d8 8c d0
[  979.756755] successfully emulated instruction
[  979.757427] Failed vm entry (exit reason 0x21) invalid guest state
[  979.757430] emulation at (46e56) rip 6e16: 8c d0 81 e4
[  979.757433] successfully emulated instruction
[  979.758074] Failed vm entry (exit reason 0x21) invalid guest state
[  979.758077] emulation at (46e58) rip 6e18: 81 e4 ff ff


The corresponding gfxboot code is:

 16301 00006E0B EA[106E]1800                    jmp 
pm_seg.prog_c32:switch_to_pm_20
 16302                                  switch_to_pm_20:
 16303                                 
 16304                                          bits 32
 16305                                 
 16306 00006E10 66B82000                        mov ax,pm_seg.prog_d16
 16307 00006E14 8ED8                            mov ds,ax
 16308                                 
 16309 00006E16 8CD0                            mov eax,ss
 16310 00006E18 81E4FFFF0000                    and esp,0ffffh
 

The VT state should be correct after executing instruction an RIP 6E16 
(mov eax, ss).  The next instruction should not cause a vmentry 
failure.  The fact that it is for you indicates that you're not updating 
guest state correctly.

My guess would be that load_segment_descriptor is not updating the 
values within the VMCS.

Regards,

Anthony Liguori