[Qemu-devel] Re: POLL: Why do you use kqemu?

[Avi Kivity <avi@redhat.com>]

Jan Kiszka wrote:
>> When kvm write protects a guest page table in the shadow page table
>> entries pointing to that guest page, it should also write protect the
>> guest page table in the host page table entries to the same guest page.
>>     
>
> Ah, now I got it. What do other hypervisors do?
>   

As far as I can tell, Xen's head is in the sand too.  No idea about 
others.  I think qemu/tcg is fine.

>>> Does this still apply to nested paging? I guess (hope) not...
>>>   
>>>       
>> No, nested paging brings cancer and cures world peace.  Or something.
>>
>>     
>
> Well, then it's probably not worth bothering, at least until a real
> guest problem is explainable with this limitation. 

I agree.

> Are there any
> suspicious reports floating around (maybe not only about Windows)?
>   

Not that I'm aware of.  Paging page tables is tricky business.  Given 
that the pointed-to pages may have been evicted while the page table was 
in swap, I guess a guest would have to revalidate the entries anyway, 
thus triggering re-shadowing.

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