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Re: [Xen-devel] [PATCH v3 0/3] map grant refs at pfn = mfn

On 24/07/14 14:30, Stefano Stabellini wrote:
Hi all,
this patch series introduces a second p2m mapping of grant reference on
ARM at guest physical address == machine address of the grant ref.  It
is safe because dom0 is already mapped 1:1. We export
XENFEAT_grant_map_identity to signal the guest that this second p2m
mapping is

One reason for wanting the second p2m mapping is to avoid tracking mfn
to pfn mappings in the guest kernel. Since the same mfn can be granted
multiple times to the backend, finding the right pfn corresponding to a
given mfn can be difficult and expensive. Providing a second mapping at
a known address allow the kernel to access the page without knowing the

Is there a version of these patches for Xen 4.4 that I can test? The restriction on duplicate pages is causing trouble for networking on Mirage (http://roscidus.com/blog/blog/2014/07/28/my-first-unikernel/#tcp-retransmissions).

Changes in v3:
- add "introduce is_domain_direct_mapped(d) as (0) on x86";
- use p2m_iommu types in arch_grant_(un)map_page_identity;
- call arch_grant_(un)map_page_identity functions from
- introduce gnttab_need_identity_mapping;
- check gnttab_need_identity_mapping in __gnttab_map_grant_ref and

Stefano Stabellini (3):
       xen/x86: introduce is_domain_direct_mapped(d) as (0) on x86
       xen: introduce arch_grant_(un)map_page_identity
       xen/arm: introduce XENFEAT_grant_map_identity

  xen/arch/arm/p2m.c                 |   22 ++++++++++++++++++++++
  xen/common/grant_table.c           |   35 +++++++++++++++++++++++++++--------
  xen/common/kernel.c                |    3 +++
  xen/drivers/passthrough/arm/smmu.c |   13 ++-----------
  xen/include/asm-arm/grant_table.h  |    3 +++
  xen/include/asm-arm/p2m.h          |    4 ++++
  xen/include/asm-x86/domain.h       |    1 +
  xen/include/asm-x86/grant_table.h  |    2 ++
  xen/include/asm-x86/p2m.h          |   13 +++++++++++++
  xen/include/public/features.h      |    3 +++
  10 files changed, 80 insertions(+), 19 deletions(-)

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