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Re: [Xen-devel] RFC: [0/2] Remove netloop by lazy copying in netback

On 27/3/07 08:44, "Herbert Xu" <herbert@xxxxxxxxxxxxxxxxxxx> wrote:

> There is another way.  Instead of expanding add_to_physmap which
> doesn't quite fit our semantics, let's add a new operation that
> *actually* swaps two p2m entries.  Then it can be used as follows:
>         a) new_addr = alloc_page
>         b) memcpy(new_addr, addr, len)
>         c) p2m_swap(__pa(new_addr), __pa(addr))
>         d) grant_unmap(__pa(new_addr))

I like this a bit more than the grant-table hypercall, mainly because I
suspect the hypercall implementation is simpler. I'm not sure how easy it is
to make atomic though! Would there be enough locking to ensure that one of
the p2m entries being present in both (or neither) locations at some
intermediate point in time would not matter?

 -- Keir

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