Re: switching from KVM guest to the host .... TLBs not present?

[Avi Kivity <avi@redhat.com>]

Zhang, Xiantao wrote:
> Jes Sorensen wrote:
>   
>> Zhang, Xiantao wrote:
>>     
>>> Yeah, that is very strange! I will check it tomorrow, and have to
>>> sleep now :-) Xiantao
>>>       
>> Hi Xiantao,
>>
>> I think I got it!
>>
>> We were calling local_irqs_disable() before calling down_read(), but
>> down_read() can sleep and so may return with local interrupts
>> re-enabled.....
>>
>> I have reordered things so now we should be safe.
>>
>> How does this patch look to you?
>>     
>
> Good catch! That should be root-cause. The patch seems good! Thanks!
> Acked-by: Xiantao Zhang <xiantao.zhang@intel.com>
>
> Avi, 
>    Please queue it as the fix of 2.6.30. Thanks!
>   

Applied, but I note that entering the guest with any lock held is 
problematic, as the guest may spend an arbitrary amount of time in guest 
mode.  Really, entering the guest is almost exactly like exiting to 
userspace.

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