Re: [PATCH v2 2/6] KVM: MMU: don't drop spte if overwrite it from W to RO

[Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>]

On 11/17/2010 11:57 PM, Avi Kivity wrote:

>>>   set_pte:
>>>       update_spte(sptep, spte);
>>> +    /*
>>> +     * If we overwrite a writable spte with a read-only one we
>>> +     * should flush remote TLBs. Otherwise rmap_write_protect
>>> +     * will find a read-only spte, even though the writable spte
>>> +     * might be cached on a CPU's TLB.
>>> +     */
>>> +    if (is_writable_pte(entry)&&  !is_writable_pte(*sptep))
>>> +        kvm_flush_remote_tlbs(vcpu->kvm);
>> There is no need to flush on sync_page path since the guest is
>> responsible for it.
>>
> 
>  If we don't, the next rmap_write_protect() will incorrectly decide that
> there's no need to flush tlbs.
> 

Maybe it's not a problem if guest can flush all tlbs after overwrite it?
Marcelo, what's your comment about this?