[for-4.7 1/2] xen: XENMEM_add_physmap_batch: Mark 'foreign_id' as reserved for dev_mmio

[Julien Grall <julien.grall@arm.com>]

The field 'foreign_id' is not used when the space is dev_mmio. As the
space is not yet part of the stable ABI, the field is marked as reserved
for future use.

The value should always be 0, other values will return -ENOSYS.

Note that the code would need some rework (such as renaming the field
'foreign_id' to a generic name), however the release of Xen 4.7 is
really close. The rework will be done for the next release.

Signed-off-by: Julien Grall <julien.grall@arm.com>
---
 xen/arch/arm/mm.c           | 4 ++++
 xen/common/memory.c         | 6 ++++--
 xen/include/public/memory.h | 2 +-
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index b46e23e..83edfa1 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -1143,6 +1143,10 @@ int xenmem_add_to_physmap_one(
         break;
     }
     case XENMAPSPACE_dev_mmio:
+        /* The field 'foreign_domid' is reserved for future use */
+        if ( foreign_domid )
+            return -ENOSYS;
+
         rc = map_dev_mmio_region(d, gpfn, 1, idx);
         return rc;
 
diff --git a/xen/common/memory.c b/xen/common/memory.c
index 644f81a..6bc52ac 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -639,9 +639,11 @@ static int xenmem_add_to_physmap(struct domain *d,
 {
     unsigned int done = 0;
     long rc = 0;
+    /* The field 'foreign_id' should be 0 when mapping MMIO. */
+    domid_t inv = (xatp->space != XENMAPSPACE_dev_mmio) ? DOMID_INVALID : 0;
 
     if ( xatp->space != XENMAPSPACE_gmfn_range )
-        return xenmem_add_to_physmap_one(d, xatp->space, DOMID_INVALID,
+        return xenmem_add_to_physmap_one(d, xatp->space, inv,
                                          xatp->idx, xatp->gpfn);
 
     if ( xatp->size < start )
@@ -658,7 +660,7 @@ static int xenmem_add_to_physmap(struct domain *d,
 
     while ( xatp->size > done )
     {
-        rc = xenmem_add_to_physmap_one(d, xatp->space, DOMID_INVALID,
+        rc = xenmem_add_to_physmap_one(d, xatp->space, inv,
                                        xatp->idx, xatp->gpfn);
         if ( rc < 0 )
             break;
diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h
index fe52ee1..b023046 100644
--- a/xen/include/public/memory.h
+++ b/xen/include/public/memory.h
@@ -259,7 +259,7 @@ struct xen_add_to_physmap_batch {
 
     /* Number of pages to go through */
     uint16_t size;
-    domid_t foreign_domid; /* IFF gmfn_foreign */
+    domid_t foreign_domid; /* IFF gmfn_foreign. Should be 0 for other spaces. */
 
     /* Indexes into space being mapped. */
     XEN_GUEST_HANDLE(xen_ulong_t) idxs;
-- 
1.9.1


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