Re: [PATCH] mask out clflush

[Anthony Liguori <anthony@codemonkey.ws>]

Avi Kivity wrote:
> Anthony Liguori wrote:
>> Yang, Sheng wrote:
>>> On Wednesday 09 July 2008 02:29:44 Glauber Costa wrote:
>>>  
>>>> clflush is a non-privileged instruction that flushes the cacheline
>>>> given by its parameter, in terms of linear address. As it is
>>>> non-privileged, it is quite tricky, because a guest doing clflush
>>>> will actually be trying to flush a host kernel address.
>>>>     
>>>
>>> The linear address was convert to host physical address, then cache 
>>> line was flushed. Of course the host physical address was used by 
>>> guest at the time. I don't understand why we need to prevent guest 
>>> from flushing cache line related to itself...
>>>   
>>
>> The problem turned out to be that we aren't emulating clflush in 
>> x86_emulate.
>>
>
> Why would clflush trap?  Is it called from real mode?

It's equivalent to a read from a VT perspective so if the read would 
trap, the clflush instruction will trap.

Regards,

Anthony Liguori