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




Ping, any input for X86 maintainers (Keir, Jan)?

On 11/14/2013 04:18 PM, Julien Grall wrote:


On 11/14/2013 03:34 PM, Stefano Stabellini wrote:
On Thu, 14 Nov 2013, Julien Grall wrote:
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@xxxxxxxxxx>
CC: Keir Fraser <keir@xxxxxxx>
CC: Jan Beulich <jbeulich@xxxxxxxx>
---
  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

I don't know if the x86 maintainers would like that, but I would prefer
to remove the ifdef CONFIG_ARM.
You just need to define a new function called is_dom0_mapped_11, that
always returns false on x86 and on ARM is implemented by d == dom0 &&
platform_has_quirk(PLATFORM_QUIRK_DOM0_MAPPING_11).
Then you can use it on common code.

With this solution, it's less clear that it's ARM specific code. We are
introducing a workaround that will never be used on x86.

I would wait an opinion from other maintainers before sending a new
version of this patch.


--
Julien Grall

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