Re: [Xen-devel] [PATCH 2 of 3] x86/mm: Teach paging to page table-based p2m

[Tim Deegan <tim@xxxxxxx>]

At 08:46 -0700 on 15 Mar (1331801170), Andres Lagar-Cavilla wrote:
> > Righto.  In that case, I'd be happy with just clipping MFNs and not
> > trying to unpack them.  But I think it should happen in the main
> > pte-building macros, not scattered around the p2m code.  It should just
> > be a matter of using PADDR_MASK in the right place.
> 
> Something along these lines? (RFC, not tested yet)
> Andres
> 
>  /* Construct a pte from a pfn and access flags. */
>  #define l1e_from_pfn(pfn, flags)   \
> -    ((l1_pgentry_t) { ((intpte_t)(pfn) << PAGE_SHIFT) | put_pte_flags(flags) 
> })
> +    ((l1_pgentry_t) { ((intpte_t)((pfn) & (PADDR_MASK >> PAGE_SHIFT)) <<   \
> +                        PAGE_SHIFT) | put_pte_flags(flags) })

Yes, that's the idea.  I think 

> +    ((l1_pgentry_t) { (((intpte_t)(pfn) << PAGE_SHIFT) & PADDR_MASK) \
> +                       | put_pte_flags(flags) })

is a little neater, maybe?

In any case, I'd like Keir's ack on this, since it will affect all the
PV pagetable code too (hopefully in a trivial and correct way).

Tim.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel