Re: [PATCH 2/2] x86: Bail out on unemulated instructions

[Avi Kivity <avi@redhat.com>]

  On 08/15/2010 03:43 PM, Mohammed Gamal wrote:
> 2010/8/15 Gleb Natapov<gleb@redhat.com>:
>> On Sun, Aug 15, 2010 at 03:40:00PM +0300, Mohammed Gamal wrote:
>>> On Sun, Aug 15, 2010 at 10:32 AM, Gleb Natapov<gleb@redhat.com>  wrote:
>>>> On Sat, Aug 14, 2010 at 06:51:34PM +0300, Mohammed Gamal wrote:
>>>>> If emulation fails due to the instruction being unemulated. Return immediately
>>>>> instead of restarting the instruction and infinitely trying to execute it.
>>>>>
>>>> This is already handled correctly as far as I can see. Sometimes
>>>> instruction should be retried and reexecute_instruction() checks
>>>> for that case. If instruction emulation fails in big real mode
>>>> re-executing instruction will be useless though, so what should be done
>>>> is to make reexecute_instruction() return false if vcpu is in big real
>>>> mode and cpu relies on emulation to handle it.
>>> We don't have a separate mode for big real mode. The emulation modes
>>> we have are real and vm86
>>>
>> That doesn't makes the patch right. So we will have to figure something
>> out.
> True. Can we do it for real mode in general (i.e. X86EMUL_MODE_REAL)?

We can do it conditionally for CPL=0.  That includes real mode (and 
excludes vm86).

However, there's a race involved (see a895e576cfd96).  I don't see how 
we can call handle_emulation_failure() without opening the race again.

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