[PATCH] xen/arm: Allow balooning working with 1:1 memory mapping

[Julien Grall <julien.grall@linaro.org>]

With the lake of iommu, dom0 must have a 1:1 memory mapping for all
these guest physical address. When the ballon decides to give back a
page to the kernel, this page must have the same address as previously.
Otherwise, we will loose the 1:1 mapping and will break DMA-capable
device.

Signed-off-by: Julien Grall <julien.grall@linaro.org>
CC: Keir Fraser <keir@xen.org>
CC: Jan Beulich <jbeulich@suse.com>
---
 xen/common/memory.c | 42 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 40 insertions(+), 2 deletions(-)

diff --git a/xen/common/memory.c b/xen/common/memory.c
index 50b740f..df36d43 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -28,6 +28,9 @@
 #include <public/memory.h>
 #include <xsm/xsm.h>
 #include <xen/trace.h>
+#ifdef CONFIG_ARM
+#include <asm/platform.h>
+#endif
 
 struct memop_args {
     /* INPUT */
@@ -90,7 +93,7 @@ static void increase_reservation(struct memop_args *a)
 
 static void populate_physmap(struct memop_args *a)
 {
-    struct page_info *page;
+    struct page_info *page = NULL;
     unsigned long i, j;
     xen_pfn_t gpfn, mfn;
     struct domain *d = a->domain;
@@ -122,7 +125,33 @@ static void populate_physmap(struct memop_args *a)
         }
         else
         {
-            page = alloc_domheap_pages(d, a->extent_order, a->memflags);
+#ifdef CONFIG_ARM
+            if ( d == dom0 && platform_has_quirk(PLATFORM_QUIRK_DOM0_MAPPING_11) )
+            {
+                mfn = gpfn;
+                if (!mfn_valid(mfn))
+                {
+                    gdprintk(XENLOG_INFO, "Invalid mfn 0x%"PRI_xen_pfn"\n",
+                             mfn);
+                    goto out;
+                }
+
+                page = mfn_to_page(mfn);
+                if ( !get_page(page, d) )
+                {
+                    gdprintk(XENLOG_INFO,
+                             "mfn 0x%"PRI_xen_pfn" doesn't belong to dom0\n",
+                             mfn);
+                    goto out;
+                }
+                put_page(page);
+            }
+            else
+#endif
+            {
+                page = alloc_domheap_pages(d, a->extent_order, a->memflags);
+            }
+
             if ( unlikely(page == NULL) ) 
             {
                 if ( !opt_tmem || (a->extent_order != 0) )
@@ -270,6 +299,15 @@ static void decrease_reservation(struct memop_args *a)
              && p2m_pod_decrease_reservation(a->domain, gmfn, a->extent_order) )
             continue;
 
+#ifdef CONFIG_ARM
+        /* With the lake for iommu, dom0 must retrieve the same pfn when
+         * the hypercall populate_physmap is called.
+         */
+        if ( a->domain == dom0 &&
+             platform_has_quirk(PLATFORM_QUIRK_DOM0_MAPPING_11) )
+            continue;
+#endif
+
         for ( j = 0; j < (1 << a->extent_order); j++ )
             if ( !guest_remove_page(a->domain, gmfn + j) )
                 goto out;
-- 
1.8.3.1