Re: [PATCH][RESEND] x86_emulator: Emulate cld and std instruction

[Avi Kivity <avi@qumranet.com>]

Mohammed Gamal wrote:
> On Thu, Jul 31, 2008 at 12:57 PM, Avi Kivity <avi@qumranet.com> wrote:
>   
>> Mohammed Gamal wrote:
>>     
>>> This patch adds 'cld' and 'std' instructions to the emulator
>>>
>>>
>>>       
>> I presume for big real mode?  Which guest wants it?
>>     
>
> Actually I was experimenting with checking guest state and emulating
> on mode switches. When I was doing so, it used to happen with all
> guests, so I guess it maybe something related to the BIOS not a
> specific guest.
>   

There is indeed a cld in rombios.c (after rombios32_05), but it appears 
to be after all segments have been initialized.

> BTW, the other way we can do is still handle vmentry failures. I
> discovered that the problem that caused occasional exits with
> Guillaume's patches is very likely to be that not enough checks on the
> guest state.
>
> The only check was if CS RPL equals SS RPL, so what happens is that
> when a vmexit and then a vmentry occurs CS and SS RPL maybe equal, but
> other checks might cause a vmentry failure. I've written a function to
> check that guest state is VMX valid - although not all checks are
> implemented yet, and I no more get the occasional vmexits.
>   

I'm still worried about undoing the interrupt injection setup.

-- 
error compiling committee.c: too many arguments to function