Re: [Xen-devel] [PATCH] fix memory exchange hypercall.

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

On Thu, Mar 15, 2007 at 12:23:20PM +0000, Keir Fraser wrote:
> Whichever, I think we should sort it out one way or the other and change
> ia64 and/or x86 now. Or it'll never happen!

I see. To be honest I expected this kind of response.
I'll give it a try again, but it may take a while.

Could you explain about PGC_allocated and balloon?
What's the rationale when to clear/set PGC_allocate bit?

My understanding is as follows.
- PGC_allocated means +1 page reference count.
- It is neccessary for x86 paravirtualized domain to keep
  page from freeing.
- It doesn't make sense for x86 hvm domain so that it is only cleared
  by relinquish_memory().
- If the p2m entry is cleared which isn't followed by
  clearing PGC_allocaed and put_page() without any recording,
  there is no easy way to free the page until domain destruction.

thnaks,
-- 
yamahata

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