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Re: [Xen-devel] [PATCH v2] xen/arm: Allow balooning working with 1:1 memory mapping





On 12/16/2013 12:11 PM, Stefano Stabellini wrote:
On Mon, 16 Dec 2013, Jan Beulich wrote:
On 13.12.13 at 21:18, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -90,7 +90,7 @@ 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;

Why?

@@ -122,7 +122,29 @@ static void populate_physmap(struct memop_args *a)
          }
          else
          {
-            page = alloc_domheap_pages(d, a->extent_order, a->memflags);
+            if ( d == dom0 && is_dom0_mapped_11() )
+            {
+                mfn = gpfn;
+                if (!mfn_valid(mfn))

Coding style.

+                {
+                    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);
+            }

I think this hack doesn't belong into a common file. Rather than
having the (anyway oddly named) is_dom0_mapped_11(), it
would seem more clean to have this implemented by an inline
function for ARM, returning the struct page_info * (and getting
#define-d to NULL for all other cases, perhaps not even in an
x86 header, but right in the source file).

Considering that having a 1:1 mapping for dom0 is conceivable even on
x86 (if you want PVH dom0 but your platform doesn't come with an IOMMU),
I would prefer the approach taken here. However I find your alternative
suggestion acceptable too.

I will stay on your solution, with is_dom0_mapped_11 modify to is_domain_direct_mapped().

--
Julien Grall

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