Re: [Xen-devel] [PATCH RFC 6/9] xen: arm: handle variable p2m levels in p2m_lookup

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2014-07-31 at 12:14 +0100, Julien Grall wrote:
> > +        if ( level == 3 && !p2m_table(pte) )
> > +            /* Invalid, clobber the pte */
> > +            pte.bits = 0;
> > +        if ( level == 3 || !p2m_table(pte) )
> > +            /* Done */
> > +            break;
> >  
> > -    BUILD_BUG_ON(THIRD_MASK != PAGE_MASK);
> > +        BUG_ON(level == 3);
> 
> Rather than checking level == 3, I would add
> BUG_ON(level < 4) at the end of loop.

You mean outside/before the loop?

That doesn't work if we hit a superpage mapping, since we will exit the
loop with level < 4. I think it needs to stay where it is.

> The only drawback to be there is we map one more page.
> 
> And same remark as the previous BUG_ON().

I did make it an ASSERT(level < 3) though.

Ian.


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