Re: [Xen-devel] [V6 PATCH 6/7] pvh dom0: Add and remove foreign pages

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 12/06/2013 02:38 AM, Mukesh Rathor wrote:
> In this patch, a new function, xenmem_add_foreign_to_p2m(), is added
> to map pages from foreign guest into current dom0 for domU creation.
> Such pages are typed p2m_map_foreign. Also, support is added here to
> XENMEM_remove_from_physmap to remove such pages. Note, in the remove
> path, we must release the refcount that was taken during the map phase.
>
> Signed-off-by: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
> ---
>   xen/arch/x86/mm.c         |   88 +++++++++++++++++++++++++++++++++++++++++----
>   xen/common/memory.c       |   37 ++++++++++++++++++-
>   xen/include/asm-arm/p2m.h |    2 +
>   3 files changed, 118 insertions(+), 9 deletions(-)
This patch doesn't compile on ARM:
memory.c: In function 'do_memory_op':
memory.c:682:20: error: unused variable 'p2mt' [-Werror=unused-variable]
cc1: all warnings being treated as errors

For x86, when a domain is destroyed and there is still some foreign page 
mapped, you forget to decrease the refcount (via put_page). It will 
likely result to a zombie domain.
For instance a stubdomain with foreign map on a guest. If the stubdomain 
doesn't release the page, this guest will become a zombie.
--
Julien Grall

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