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Re: [Xen-devel] [PATCH v2 1/2] xen: introduce arch_iommu_grant_(un)map_page

On 24/07/14 12:07, Stefano Stabellini wrote:
On Thu, 24 Jul 2014, Julien Grall wrote:
Hi Stefano,

The Title of the commit message is now wrong.

Thanks, I didn't notice.

On 23/07/14 18:19, Stefano Stabellini wrote:
Introduce two arch specific functions to create a new p2m mapping of
granted pages at pfn == mfn.
The x86 implementation just returns ENOSYS.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
   xen/arch/arm/p2m.c        |   19 +++++++++++++++++++
   xen/include/asm-arm/p2m.h |    4 ++++
   xen/include/asm-x86/p2m.h |   13 +++++++++++++
   3 files changed, 36 insertions(+)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 9960e17..c38af59 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -555,6 +555,25 @@ void guest_physmap_remove_page(struct domain *d,
                         pfn_to_paddr(mfn), MATTR_MEM, p2m_invalid);

+int arch_grant_map_page_identity(struct domain *d, unsigned long frame,
+                                 bool_t writeable)
+    p2m_type_t t;
+    if ( writeable )
+        t = p2m_ram_rw;
+    else
+        t = p2m_ram_ro;

This is not the right p2m type to use here. p2m_ram_{rw,ro} allow foreign
mapping. So another guest could access to the grant.

I would use p2m_iommu_map_{rw,ro}.

I see. I'll make the change and add a comment to explain why we are
using p2m_iommu types for non-iommu related mappings.

The code to add the 1:1 mapping for the SMMU is very ugly. I was wondering if we could drop the iommu_map_page callback and
directly use arch_grant_map_page_identity in all the case.

It would avoid the if/else in the grant code.


Julien Grall

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