Re: [patch 3/5] KVM: add kvm_follow_page()

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Andrew Morton wrote:
> On Sun, 23 Dec 2007 10:59:22 +0200 Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org> wrote:
>
>   
>> Avi Kivity wrote:
>>     
>>> Avi Kivity wrote:
>>>   
>>>       
>>>> Exactly.  But it is better to be explicit about it and pass the page
>>>> directly like you did before.  I hate to make you go back-and-fourth,
>>>> but I did not understand the issue completely before.
>>>>
>>>>     
>>>>         
>>> btw, the call to gfn_to_page() can happen in page_fault() instead of
>>> walk_addr(); that will reduce the amount of error handling, and will
>>> simplify the callers to walk_addr() that don't need the page.
>>>
>>>   
>>>       
>> Note further that all this doesn't obviate the need for follow_page()
>> (or get_user_pages_inatomic()); we still need something in update_pte()
>> for the demand paging case.
>>     
>
> Please review -mm's mm/pagewalk.c for suitability.
>
> If is is unsuitable but repairable then please cc Matt Mackall
> <mpm-VDJrAJ4Gl5ZBDgjK7y7TUQ@public.gmane.org> on the review.
>
>   

The "no locks are taken" comment is very worrying.  We need accurate 
results.

Getting pte_t's in the callbacks is a little too low level for kvm's use 
(which wants struct page pointers) but of course that easily handled in 
a kvm wrapper.

I'd prefer an atomic version of get_user_pages(), but if pagewalk is 
fixed to take the necessary locks, it will do.


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


-------------------------------------------------------------------------
This SF.net email is sponsored by: Microsoft
Defy all challenges. Microsoft(R) Visual Studio 2005.
http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/