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Re: [Xen-devel] [PATCH v4 1/4] xen: introduce a helper to allocate non-contiguous memory

At 16:22 +0100 on 07 May (1431015746), Tim Deegan wrote:
> At 16:29 +0200 on 07 May (1431016173), Roger Pau Monne wrote:
> > The allocator uses independent calls to alloc_heap_pages in order to get the
> > desired amount of memory and then maps all the independent physical
> > addresses into a contiguous virtual address space.
> > 
> > In order to keep track of this regions a red-black tree is used.
> On x86, at least, the vmap apparatus should be able to tell you what
> MFN is mapped by using the linear map to look at the l1e.  On ARM, it
> looks like we could walk the xen pagetable trie from xen_second[] for
> the same effect.
> So I'd suggest adding a vmap_to_mfn() and usign that instead of
> building the red-black tree. 

Also: does this need a clear_page() somewhere to scrub the allocation?
If not here, I think it's needed in patches 2 and 3 where you're
replacing xzalloc (unless you're sure that the loop will write every
byte of the allocation, in which case xzalloc was overkill).


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