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

[Thomas Leonard <talex5@gmail.com>]

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
> available.
>
> 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
> pfn.

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
> arm_smmu_(un)map_page;
> - introduce gnttab_need_identity_mapping;
> - check gnttab_need_identity_mapping in __gnttab_map_grant_ref and
> __gnttab_unmap_common.
>
>
>
> 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(-)
>