[Xen-devel] page refcount on pages mapped by the toolstack..

[Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>]

Hi,

I observed something that doesn't seem right to me:

PV dom0 booting PV guest (say domid 1). (no PVH).

xl cr vm.cfg.pv

Take some mfn from domid 1. It's refcnt is 1 as expected. Now, the lib
wants to map it via xen_remap_domain_mfn_range(). The call goes thru
do_mmu_update(), and upon returning the refcnt is 2, as expected.

Now, I noticed the refcnt doesn't go back to 1 after the guest is 
created/booted. I'd have expected the process exit somewhere to have
resulted in the refcnt going down to 1 (which is what would happen in case
of PVH dom0).

The guest is up, I notice the refcnt is 2. I shutdown the guest, the
refcnt goes to 0 and the page is freed via relinquish_memory() called
from domain_relinquish_resources(). I would have expected the page
to hang with refcnt 1, what if the user process still has it mapped?

What am I missing?

Thanks,
Mukesh


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