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Re: [Xen-devel] [for-4.7 2/2] xen/arm: Document the behavior of XENMAPSPACE_dev_mmio

Hi Jan,

On 25/05/16 14:14, Jan Beulich wrote:
On 25.05.16 at 13:41, <julien.grall@xxxxxxx> wrote:
--- a/xen/include/public/memory.h
+++ b/xen/include/public/memory.h
@@ -220,7 +220,10 @@ DEFINE_XEN_GUEST_HANDLE(xen_machphys_mapping_t);
  #define XENMAPSPACE_gmfn_range   3 /* GMFN range, XENMEM_add_to_physmap only. 
  #define XENMAPSPACE_gmfn_foreign 4 /* GMFN from another dom,
                                      * XENMEM_add_to_physmap_batch only. */
-#define XENMAPSPACE_dev_mmio     5 /* device mmio region */
+#define XENMAPSPACE_dev_mmio     5 /* device mmio region
+                                      On ARM, the region will be mapped
+                                      in stage-2 using the memory attribute
+                                      Device_nGnRE. */

Since this is unimplemented on x86, may I suggest to make this "ARM
only; the region will be ..."?

Sounds good.

Also - is Device_nGnRE a term uniform between ARM32 and ARM64?

Actually it should be Device-nGnRE to match with the spec. This has been introduced on Armv8. Previously for Armv7, the name was "Device", although the behavior is exactly the same.

I could say:

"ARM only; the region will be mapped in Stage-2 using the memory attribute 'Device-nGnRE' (previously named 'Device' on ARMv7)".


Julien Grall

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