arm/xen: implement correctly pfn_to_mfn

After the commit introducing convertion between DMA and guest addresses,
all the callers of pfn_to_mfn are expecting to get a GFN (Guest Frame
Number). On ARM, all the guests are auto-translated so the GFN is equal
to the Linux PFN (Pseudo-physical Frame Number).

The current implementation may return an MFN if the caller is passing a
PFN associated to a mapped foreign grant. In pratice, I haven't seen
the problem on running guest but we should fix it for the sake of
correctness.

Correct the implementation by always returning the pfn passed in parameter.

A follow-up patch will take care to rename pfn_to_mfn to a suitable
name.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
(cherry picked from commit 5192b35de47e47a0f736fe30da199f32030680e7)
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h
index 5f76a9e7ef1b7aca462c46b4451a2ab78ba06c50..911d62b4df26eea29c1a57d417ffda3cc434205c 100644 (file)
--- a/arch/arm/include/asm/xen/page.h
+++ b/arch/arm/include/asm/xen/page.h
@@ -36,14 +36,6 @@ extern struct rb_root phys_to_mach;
 
 static inline unsigned long pfn_to_mfn(unsigned long pfn)
 {
-       unsigned long mfn;
-
-       if (phys_to_mach.rb_node != NULL) {
-               mfn = __pfn_to_mfn(pfn);
-               if (mfn != INVALID_P2M_ENTRY)
-                       return mfn;
-       }
-
        return pfn;
 }