Re: [Xen-devel] Could the page sharing inside domain? (memory_sharing on xen)

[Jui-Hao Chiang <juihaochiang@xxxxxxxxx>]

Hi,

The error messages you see above are from dom0 trying to map dom4's
memory and finding a shared page (i.e. owned by dom_cow).  Either
there's a missing unshare operation on the path that called
get_page_from_l1e(), or a race where a page got re-shared before the
mapping could be completed, or possibly the unshare operation doesn't
work properly when a domain has two copies of a shared page.

Tim.

That's exactly what we have found during yesterday.
It is because the code doesn't update/check p2m type with the shr_lock, which causes either incorrect share operation or race-condition in unshare operation.
We will submit our current fix as a patch soon.

Bests,
Jui-Hao

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