Re: Question about EMULATE_DO_MMIO

[Nitin A Kamble <nitin.a.kamble-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

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On Tue, 2007-10-16 at 13:12 -0700, Avi Kivity wrote:

> Why do you think it is better?  I would have thought that vm86 is much
> faster.
> 
I am seeing execution going to strange places in vm86 mode. That issue
is not coming in the emulation.

> I thought of doing it this way:
> 
> - try to run normally
> - if vm entry failed due to invalid guest state (the famous
> 0x80000021),
> then emulate 50 instructions
> - repeat
This may be better, I will give it a try.

> That will also handle the few cases where VT can't handle protected
> mode.
> 
> It should exit to userspace, same as the non-emulating case.  However
> it
> shouldn't happen for normal writes.
> 
Only thing is if it in the real mode, then returning back to user mode
will setup the cpu state as real mode, and because of that vmenter will
fail.

> 
> --
> Do not meddle in the internals of kernels, for they are subtle and
> quick to panic.
> 
> 

Thanks a lot for your input.

-- 
Thanks & Regards,
Nitin
Open Source Technology Center, Intel Corporation
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