diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 6450850457..99201ac615 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -1222,7 +1222,7 @@ void share_xen_page_with_guest(struct page_info *page, struct domain *d,
 int xenmem_add_to_physmap_one(
     struct domain *d,
     unsigned int space,
-    union xen_add_to_physmap_batch_extra extra,
+    union add_to_physmap_extra extra,
     unsigned long idx,
     gfn_t gfn)
 {
@@ -1294,10 +1294,6 @@ int xenmem_add_to_physmap_one(
         break;
     }
     case XENMAPSPACE_dev_mmio:
-        /* extra should be 0. Reserved for future use. */
-        if ( extra.res0 )
-            return -EOPNOTSUPP;
-
         rc = map_dev_mmio_region(d, gfn, 1, _mfn(idx));
         return rc;
 
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 4ff24de73d..5ca5c8c9a2 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -4678,7 +4678,7 @@ static int handle_iomem_range(unsigned long s, unsigned long e, void *p)
 int xenmem_add_to_physmap_one(
     struct domain *d,
     unsigned int space,
-    union xen_add_to_physmap_batch_extra extra,
+    union add_to_physmap_extra extra,
     unsigned long idx,
     gfn_t gpfn)
 {
@@ -4765,9 +4765,20 @@ int xenmem_add_to_physmap_one(
         rc = guest_physmap_add_page(d, gpfn, mfn, PAGE_ORDER_4K);
 
  put_both:
-    /* In the XENMAPSPACE_gmfn case, we took a ref of the gfn at the top. */
+    /*
+     * In the XENMAPSPACE_gmfn case, we took a ref of the gfn at the top.
+     * We also may need to transfer ownership of the page reference to our
+     * caller.
+     */
     if ( space == XENMAPSPACE_gmfn )
+    {
         put_gfn(d, gfn);
+        if ( !rc && extra.ppage )
+        {
+            *extra.ppage = page;
+            page = NULL;
+        }
+    }
 
     if ( page )
         put_page(page);
diff --git a/xen/common/memory.c b/xen/common/memory.c
index 0ae60378f4..a4cf496f24 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -811,11 +811,10 @@ int xenmem_add_to_physmap(struct domain *d, struct xen_add_to_physmap *xatp,
 {
     unsigned int done = 0;
     long rc = 0;
-    union xen_add_to_physmap_batch_extra extra;
+    union add_to_physmap_extra extra = {};
+    struct page_info *pages[16];
 
-    if ( xatp->space != XENMAPSPACE_gmfn_foreign )
-        extra.res0 = 0;
-    else
+    if ( xatp->space == XENMAPSPACE_gmfn_foreign )
         extra.foreign_domid = DOMID_INVALID;
 
     if ( xatp->space != XENMAPSPACE_gmfn_range )
@@ -831,7 +830,10 @@ int xenmem_add_to_physmap(struct domain *d, struct xen_add_to_physmap *xatp,
 
 #ifdef CONFIG_HAS_PASSTHROUGH
     if ( need_iommu(d) )
+    {
         this_cpu(iommu_dont_flush_iotlb) = 1;
+        extra.ppage = &pages[0];
+    }
 #endif
 
     while ( xatp->size > done )
@@ -844,8 +846,12 @@ int xenmem_add_to_physmap(struct domain *d, struct xen_add_to_physmap *xatp,
         xatp->idx++;
         xatp->gpfn++;
 
+        if ( extra.ppage )
+            ++extra.ppage;
+
         /* Check for continuation if it's not the last iteration. */
-        if ( xatp->size > ++done && hypercall_preempt_check() )
+        if ( (++done > ARRAY_SIZE(pages) && extra.ppage) ||
+             (xatp->size > done && hypercall_preempt_check()) )
         {
             rc = start + done;
             break;
@@ -856,6 +862,7 @@ int xenmem_add_to_physmap(struct domain *d, struct xen_add_to_physmap *xatp,
     if ( need_iommu(d) )
     {
         int ret;
+        unsigned int i;
 
         this_cpu(iommu_dont_flush_iotlb) = 0;
 
@@ -863,6 +870,15 @@ int xenmem_add_to_physmap(struct domain *d, struct xen_add_to_physmap *xatp,
         if ( unlikely(ret) && rc >= 0 )
             rc = ret;
 
+        /*
+         * Now that the IOMMU TLB flush was done for the original GFN, drop
+         * the page references. The 2nd flush below is fine to make later, as
+         * whoever removes the page again from its new GFN will have to do
+         * another flush anyway.
+         */
+        for ( i = 0; i < done; ++i )
+            put_page(pages[i]);
+
         ret = iommu_iotlb_flush(d, xatp->gpfn - done, done);
         if ( unlikely(ret) && rc >= 0 )
             rc = ret;
@@ -876,6 +892,8 @@ static int xenmem_add_to_physmap_batch(struct domain *d,
                                        struct xen_add_to_physmap_batch *xatpb,
                                        unsigned int extent)
 {
+    union add_to_physmap_extra extra = {};
+
     if ( xatpb->size < extent )
         return -EILSEQ;
 
@@ -884,6 +902,19 @@ static int xenmem_add_to_physmap_batch(struct domain *d,
          !guest_handle_subrange_okay(xatpb->errs, extent, xatpb->size - 1) )
         return -EFAULT;
 
+    switch ( xatpb->space )
+    {
+    case XENMAPSPACE_dev_mmio:
+        /* res0 is reserved for future use. */
+        if ( xatpb->u.res0 )
+            return -EOPNOTSUPP;
+        break;
+
+    case XENMAPSPACE_gmfn_foreign:
+        extra.foreign_domid = xatpb->u.foreign_domid;
+        break;
+    }
+
     while ( xatpb->size > extent )
     {
         xen_ulong_t idx;
@@ -896,8 +927,7 @@ static int xenmem_add_to_physmap_batch(struct domain *d,
                                                extent, 1)) )
             return -EFAULT;
 
-        rc = xenmem_add_to_physmap_one(d, xatpb->space,
-                                       xatpb->u,
+        rc = xenmem_add_to_physmap_one(d, xatpb->space, extra,
                                        idx, _gfn(gpfn));
 
         if ( unlikely(__copy_to_guest_offset(xatpb->errs, extent, &rc, 1)) )
diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
index 24654e8e22..38002714de 100644
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -577,8 +577,22 @@ void scrub_one_page(struct page_info *);
                       &(d)->xenpage_list : &(d)->page_list)
 #endif
 
+union add_to_physmap_extra {
+    /*
+     * XENMAPSPACE_gmfn: When deferring TLB flushes, a page reference needs
+     * to be kept until after the flush, so the page can't get removed from
+     * the domain (and re-used for another purpose) beforehand. By passing
+     * non-NULL, the caller of xenmem_add_to_physmap_one() indicates it wants
+     * to have ownership of such a reference transferred in the success case.
+     */
+    struct page_info **ppage;
+
+    /* XENMAPSPACE_gmfn_foreign */
+    domid_t foreign_domid;
+};
+
 int xenmem_add_to_physmap_one(struct domain *d, unsigned int space,
-                              union xen_add_to_physmap_batch_extra extra,
+                              union add_to_physmap_extra extra,
                               unsigned long idx, gfn_t gfn);
 
 int xenmem_add_to_physmap(struct domain *d, struct xen_add_to_physmap *xatp,