Re: [Xen-devel] Re: [PATCH] Support swap a page from user space tools -- Was RE: [RFC][PATCH] Basic support for page offline

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 20/03/2009 02:52, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx> wrote:

> This requires we need to allocate the new page before the exchange call and we
> have to pass both old_mfn and new_mfn in step 5 to exchange the memory.
> However, current hypercall will always allocate a new page to replace the old
> one.
> 
> Currently I try to add a new hypercall for this purpose.
> 
> Maybe we can enhance the current XENMEM_exchange to accept a mem_flags, when
> that flag is set, the exch.out.extent_start will be the new_mfn instead of the
> gpfn, and the gpfn will be always same as corresponding gpfn in the
> exch.in.ext_start. But I do think this is a bit tricky, it change the meaning
> of exch.out.extent_start and how the gpn is pass down.

Thanks for the description. I guess I will wait for your next patch, which
should I think at least separate the foreign pagetable update hypercall from
this weird swap hypercall. Then I can comment on the new swap hypercall
perhaps getting less confused by it. I certainly don't promise to get this
in for 3.4 at this point however.

 -- Keir



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