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Re: [Xen-devel] [PATCH v6 3/3] tools/libxc: use superpages during restore of HVM guest

On Wed, Aug 30, 2017 at 04:27:19PM +0200, Olaf Hering wrote:
> On Wed, Aug 30, Wei Liu wrote:
> > As far as I can tell the algorithm in the patch can't handle:
> > 
> > 1. First pfn in a batch points to start of second 1G address space
> > 2. Second pfn in a batch points to a page in the middle of first 1G
> > 3. Guest can only use 1G ram
> In which way does it not handle it? Over-allocation is supposed to be
> handled by the "ctx->restore.tot_pages + sp->count >
> ctx->restore.max_pages" checks. Do you mean the second 1G is allocated,
> then max_pages is reached, and allocation in other areas is not possible
> anymore?


> Can this actually happen with the available senders? If not, this is
> again the missing memory map.

Probably not now, but as said, you shouldn't rely on the structure of
the stream unless it is stated in the spec.

And it can definitely happen with post-copy algorithm.

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