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

["Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>]

Keir Fraser <mailto:keir.fraser@xxxxxxxxxxxxx> wrote:
> 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

I think I have split that patch last night. There is no foreign page table 
hypercall anymore, instead, I just tried to enhance the current mmu_op. And 
this new "weird" swap is now named mmu_ext_exchange_page.(Is it really so weird 
to just pass the new mfn down?)

> 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.

That's ok and should depends on our discussion. Just stated before, hope check 
in IF it pass the review. Now it is on-going still :)

> 
> -- Keir
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